Fix inline asm for ci_write_xx
Fix inline asm for ci_write_xx

It was clobbering r4 and not marking it as such, causing
problems among others in virtio-blk

Signed-off-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>

stefanberger/SLOF-tpm,stefanberger/SLOF-tpm,agraf/SLOF,open-power-host-os/slof,leilihh/SLOF,open-power-host-os/slof,qemu/SLOF,k0da/SLOF,dgibson/SLOF,aik/SLOF,agraf/SLOF,leilihh/SLOF,mdroth/SLOF,dgibson/SLOF,open-power-host-os/slof,open-power-host-os/slof,k0da/SLOF,leilihh/SLOF,leilihh/SLOF,mdroth/SLOF,stefanberger/SLOF-tpm,qemu/SLOF,dgibson/SLOF,aik/SLOF,k0da/SLOF,dgibson/SLOF,k0da/SLOF,agraf/SLOF,qemu/SLOF,mdroth/SLOF,aik/SLOF,agraf/SLOF,mdroth/SLOF