KVM: arm64: Add new (V)TCR_EL2 field definitions for FEAT_LPA2

As per Arm ARM (0487I.a), (V)TCR_EL2.DS fields control whether 52 bit
input and output addresses are supported on 4K and 16K page size
configurations when FEAT_LPA2 is known to have been implemented.

This adds these field definitions which will be used by KVM when
FEAT_LPA2 is enabled.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>