xen: arm: refactor co-pro and sysreg reg handling.

xen: arm: refactor co-pro and sysreg reg handling.

AArch64 has removed the concept of co-processors replacing them with a
combination of specific instructions (cache and tlb flushes etc) and
system registers (which are understood by name in the assembler).

However most system registers are equivalent to a particular AArch32
co-pro register and can be used by generic code in the same way. Note
that the names of the registers differ (often only slightly)

For consistency it would be better to use only set of names in the
common code. Therefore move the {READ,WRITE}_CP{32,64} accessors into
arm32/processor.h and provide {READ,WRITE}_SYSREG. Where the names
differ #defines will be provided on 32-bit.

HSR_CPREG and friends are required even on 64-bit in order to decode
traps from 32 bit guests.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>