[efr32] fix build casting warnings on pointer type (#2143)
[efr32] fix build casting warnings on pointer type (#2143)


chshu/openthread,chshu/openthread,librasungirl/openthread,bukepo/openthread,pvanhorn/openthread,aeliot/openthread,chshu/openthread,fbsder/openthread,mszczodrak/openthread,LeZhang2016/openthread,georgecpr/openthread,mszczodrak/openthread,vaas-krish/openthread,erja-gp/openthread,srickardti/openthread,aeliot/openthread,mszczodrak/openthread,gandreello/openthread,aeliot/openthread,abtink/openthread,erja-gp/openthread,vaas-krish/openthread,srickardti/openthread,LeZhang2016/openthread,lanyuwen/openthread,mszczodrak/openthread,georgecpr/openthread,xiaom-GitHub/openthread,chshu/openthread,aeliot/openthread,fbsder/openthread,xiaom-GitHub/openthread,mszczodrak/openthread,pvanhorn/openthread,LeZhang2016/openthread,jwhui/openthread,erja-gp/openthread,bukepo/openthread,georgecpr/openthread,erja-gp/openthread,jwhui/openthread,LeZhang2016/openthread,abtink/openthread,LeZhang2016/openthread,chshu/openthread,turon/openthread,turon/openthread,georgecpr/openthread,vaas-krish/openthread,chshu/openthread,lanyuwen/openthread,turon/openthread,srickardti/openthread,vaas-krish/openthread,xiaom-GitHub/openthread,librasungirl/openthread,openthread/openthread,aeliot/openthread,lanyuwen/openthread,pvanhorn/openthread,vaas-krish/openthread,fbsder/openthread,fbsder/openthread,xiaom-GitHub/openthread,vaas-krish/openthread,pvanhorn/openthread,pvanhorn/openthread,xiaom-GitHub/openthread,abtink/openthread,lanyuwen/openthread,openthread/openthread,librasungirl/openthread,georgecpr/openthread,srickardti/openthread,openthread/openthread,erja-gp/openthread,gandreello/openthread,lanyuwen/openthread,LeZhang2016/openthread,gandreello/openthread,abtink/openthread,bukepo/openthread,gandreello/openthread,georgecpr/openthread,erja-gp/openthread,aeliot/openthread,jwhui/openthread,pvanhorn/openthread,gandreello/openthread,bukepo/openthread,xiaom-GitHub/openthread,lanyuwen/openthread,fbsder/openthread,gandreello/openthread,openthread/openthread,fbsder/openthread,turon/openthread,librasungirl/openthread,jwhui/openthread,mszczodrak/openthread