idec: simplify buffer size calculation
idec: simplify buffer size calculation

Change-Id: Id0e20c44704ef9b0e14dcf5e71a05cea488fd95a

ttyangf/libwebp,gshORTON/webm.libwebp,rxl194/libwebp,rxl194/libwebp,rxl194/libwebp,Tekserve/libwebp,ya7lelkom/libwebp,Aexyn/libwebp,Acidburn0zzz/webm.libwebp,ttyangf/libwebp,PKRoma/libwebp,kleopatra999/webm.libwebp,kalli123/webm.libwebp,iniwf/webm.libwebp,kalli123/webm.libwebp,comoyo/gonzo-libwebp,Aexyn/libwebp,kalli123/webm.libwebp,webmproject/libwebp,keane83/BLE_IM,gshORTON/webm.libwebp,keane83/BLE_IM,abwiz0086/webm.libwebp,Suvarna1488/webm.libwebp,iniwf/webm.libwebp,jiehu5114/libwebp,jiehu5114/libwebp,Aexyn/libwebp,rxl194/libwebp,abwiz0086/webm.libwebp,cysp/libwebp,webmproject/libwebp,dumganhar/libwebp,cysp/libwebp,kim42083/webm.libwebp,matanbs/webm.libwebp,imazen/libwebp,ya7lelkom/libwebp,appunite/libwebp,yohunl/libwebp,cysp/libwebp,kalli123/webm.libwebp,ya7lelkom/libwebp,kleopatra999/webm.libwebp,zofuthan/libwebp,kim42083/webm.libwebp,Tekserve/libwebp,ericmckean/webm.libwebp,yohunl/libwebp,reimaginemedia/webm.libwebp,reimaginemedia/webm.libwebp,redengineer/libwebp,Maria1099/webm.libwebp,keane83/BLE_IM,imazen/libwebp,redengineer/libwebp,webmproject/libwebp,Tekserve/libwebp,Maria1099/webm.libwebp,Maria1099/webm.libwebp,PKRoma/libwebp,Suvarna1488/webm.libwebp,kleopatra999/webm.libwebp,cysp/libwebp,iniwf/webm.libwebp,comoyo/gonzo-libwebp,jiehu5114/libwebp,PKRoma/libwebp,ericmckean/webm.libwebp,redengineer/libwebp,Distrotech/libwebp,jacklicn/libwebp,jacklicn/libwebp,ya7lelkom/libwebp,keane83/BLE_IM,ttyangf/libwebp,rxl194/libwebp,webmproject/libwebp,dumganhar/libwebp,reimaginemedia/webm.libwebp,zofuthan/libwebp,reimaginemedia/webm.libwebp,yohunl/libwebp,kleopatra999/webm.libwebp,altogother/webm.libwebp,PKRoma/libwebp,abwiz0086/webm.libwebp,appunite/libwebp,Acidburn0zzz/webm.libwebp,matanbs/webm.libwebp,ericmckean/webm.libwebp,Distrotech/libwebp,comoyo/gonzo-libwebp,imazen/libwebp,Distrotech/libwebp,Acidburn0zzz/webm.libwebp,zofuthan/libwebp,comoyo/gonzo-libwebp,PKRoma/libwebp,Suvarna1488/webm.libwebp,Maria1099/webm.libwebp,dumganhar/libwebp,comoyo/gonzo-libwebp,altogother/webm.libwebp,jacklicn/libwebp,zofuthan/libwebp,ttyangf/libwebp,yohunl/libwebp,jacklicn/libwebp,jiehu5114/libwebp,Maria1099/webm.libwebp,ttyangf/libwebp,altogother/webm.libwebp,matanbs/webm.libwebp,appunite/libwebp,gshORTON/webm.libwebp,Acidburn0zzz/webm.libwebp,Aexyn/libwebp,redengineer/libwebp,kim42083/webm.libwebp,PKRoma/libwebp,gshORTON/webm.libwebp,imazen/libwebp,abwiz0086/webm.libwebp,comoyo/gonzo-libwebp,kim42083/webm.libwebp,zofuthan/libwebp,ericmckean/webm.libwebp,Suvarna1488/webm.libwebp,appunite/libwebp,Aexyn/libwebp,iniwf/webm.libwebp,appunite/libwebp,kalli123/webm.libwebp,redengineer/libwebp,jacklicn/libwebp,abwiz0086/webm.libwebp,iniwf/webm.libwebp,matanbs/webm.libwebp,comoyo/gonzo-libwebp,kleopatra999/webm.libwebp,keane83/BLE_IM,ericmckean/webm.libwebp,reimaginemedia/webm.libwebp,jiehu5114/libwebp,matanbs/webm.libwebp,Acidburn0zzz/webm.libwebp,webmproject/libwebp,yohunl/libwebp,imazen/libwebp,Tekserve/libwebp,altogother/webm.libwebp,ya7lelkom/libwebp,appunite/libwebp,altogother/webm.libwebp,Suvarna1488/webm.libwebp,gshORTON/webm.libwebp,kim42083/webm.libwebp