KVM: arm64: Map AArch32 cp14 register to AArch64 sysregs

Similarly to what has been done on the cp15 front, repaint the
debug registers to use their AArch64 counterparts. This results
in some simplification as we can remove the 32bit-specific
accessors.

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