xen/arm: vcpreg: Add wrappers to handle co-proc access trapped by HCR_EL2.TVM

xen/arm: vcpreg: Add wrappers to handle co-proc access trapped by HCR_EL2.TVM

A follow-up patch will require to emulate some accesses to some
co-processors registers trapped by HCR_EL2.TVM. When set, all NS EL1 writes
to the virtual memory control registers will be trapped to the hypervisor.

This patch adds the infrastructure to passthrough the access to host
registers. For convenience a bunch of helpers have been added to
generate the different helpers.

Note that HCR_EL2.TVM will be set in a follow-up patch dynamically.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>