[platform][zynq] make sure the slcr is unlocked at the right spots during boot
[platform][zynq] make sure the slcr is unlocked at the right spots during boot

For whatever reason the sequence worked out on zybo targets so that LVL_SHFTR_EN
was able to be set, but not on other targets.

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