arm64: vgic-v2: Fix guest endianness check in hVHE mode

In hVHE when running at the hypervisor, SCTLR_EL1 refers to the
hypervisor's System Control Register rather than the guest's. Make sure
to access the guest's register to determine its endianness.

Reported-by: Will Deacon <will@kernel.org>
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20250807120133.871892-4-tabba@google.com


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>