xen/pci: solve compilation error on ARM with HAS_PCI enabled

xen/pci: solve compilation error on ARM with HAS_PCI enabled

If mem-sharing, mem-paging, or log-dirty functionality is not enabled
for architecture when HAS_PCI is enabled, the compiler will throw an
error.

Move code to x86 specific file to fix compilation error.

Also, modify the code to use likely() in place of unlikley() for each
condition to make code more optimized.

No functional change intended.

Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Acked-by: Jan Beulich <jbeulich@suse.com>