ANDROID: KVM: arm64: s2mpu: Initialize MPTs to PROT_RW

Change the permissions that MPTs are initialized with from PROT_NONE to
PROT_RW. No functional change intended as the generic IOMMU code
sets permissions for the entire address space later. This will allow to
optimize boot time by only unmapping pages not available to host.

Bug: 190463801
Bug: 218012133
Signed-off-by: David Brazdil <dbrazdil@google.com>
Change-Id: Ic29ec690a84cde22a2ce8fe33e7127711c6f0f3e