x86/P2M: derive HVM-only variant from __get_gfn_type_access()

x86/P2M: derive HVM-only variant from __get_gfn_type_access()

Introduce an inline wrapper dealing with the non-translated-domain case,
while stripping that logic from the main function, which gets renamed to
p2m_get_gfn_type_access(). HVM-only callers can then directly use the
main function.

Along with renaming the main function also make its and the new inline
helper's GFN parameters type-safe.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>