ANDROID: KVM: arm64: Use 32-bit function ID for PSCI MEM_PROTECT call

The PSCI specification defines only a 32-bit function ID for the
MEM_PROTECT call used to protect against cold reboot attacks.

Fix the pKVM hypervisor invocation of MEM_PROTECT to use the 32-bit
function ID instead of the unallocated 64-bit flavour.

[ qperret: dropped the change to include/uapi/linux/psci.h as the 32 bit
  variant of the call have been introduced upstream by 3137f2e6
  ("firmware/psci: Add debugfs support to ease debugging") ]

Bug: 260316363
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I675a57419064f7f006960ca5370e9dc2d5279a90
Signed-off-by: Quentin Perret <qperret@google.com>