ANDROID: KVM: arm64: refactor vcpu_read_sys_reg and vcpu_write_sys_reg for hyp use

Move vcpu_read_sys_reg and vcpu_write_sys_reg to a shared header
to be used by hyp in protected mode.

Refactored as macros to avoid including kvm.h, which would have
been needed for struct vcpu.

No functional change intended.

Signed-off-by: Fuad Tabba <tabba@google.com>
Bug: 209580772
Change-Id: I6b949d60b1cab6aa12978e2f9b775192701990c6
Signed-off-by: Will Deacon <willdeacon@google.com>