[platform][stm32] fix a warning
[platform][stm32] fix a warning

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