KVM: arm64: Use common Set/Way sys definitions

Now that we have common definitions for the encoding of Set/Way cache
maintenance operations, make the KVM code use these, simplifying the
sys_reg_descs table.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvmarm@lists.cs.columbia.edu