[app][lkboot] fix lkb_write() for len 65536
[app][lkboot] fix lkb_write() for len 65536

M1cha/lk,grub4android/lk,srodrig1/lk,nvll/lk,grub4android/lk,sndnvaps/lk,nvll/lk,srodrig1/lk,skabet/lk,minglun-tsai/lk,skabet/lk,travisg/lk,minglun-tsai/lk,nvll/lk,srodrig1/lk,skabet/lk,sndnvaps/lk,ErikCorryGoogle/lk,travisg/lk,littlekernel/lk,GCrean/lk,littlekernel/lk,hollanderic/lkstuff,hollanderic/lkstuff,littlekernel/lk,M1cha/lk,M1cha/lk,nvll/lk,GCrean/lk,sndnvaps/lk,grub4android/lk,M1cha/lk,littlekernel/lk,ErikCorryGoogle/lk,skabet/lk,hollanderic/lkstuff,GCrean/lk,minglun-tsai/lk,M1cha/lk,ErikCorryGoogle/lk,srodrig1/lk,srodrig1/lk,travisg/lk,sndnvaps/lk,minglun-tsai/lk,GCrean/lk,nvll/lk,skabet/lk,grub4android/lk,travisg/lk,sndnvaps/lk,hollanderic/lkstuff,grub4android/lk,ErikCorryGoogle/lk,GCrean/lk