KVM: arm64: Add timer UAPI workaround to sysreg infrastructure

KVM: arm64: Add timer UAPI workaround to sysreg infrastructure

Amongst the numerous bugs that plague the KVM/arm64 UAPI, one of
the most annoying thing is that the userspace view of the virtual
timer has its CVAL and CNT encodings swapped.

In order to reduce the amount of code that has to know about this,
start by adding handling for this bug in the sys_reg code.

Nothing is making use of it yet, as the code responsible for userspace
interaction is catching the accesses early.

Signed-off-by: Marc Zyngier <maz@kernel.org>