arm64: KVM: Avoid setting the upper 32 bits of VTCR_EL2 to 1

arm64: KVM: Avoid setting the upper 32 bits of VTCR_EL2 to 1

Although bit 31 of VTCR_EL2 is RES1, we inadvertently end up setting all
of the upper 32 bits to 1 as well because we define VTCR_EL2_RES1 as
signed, which is sign-extended when assigning to kvm->arch.vtcr.

Lucky for us, the architecture currently treats these upper bits as RES0
so, whilst we've been naughty, we haven't set fire to anything yet.

Cc: <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Christoffer Dall <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>