xen: arm: Log a warning message when a deprecated hypercall is used

xen: arm: Log a warning message when a deprecated hypercall is used

A few folks have been caught out by OSes which call e.g.
HYPERVISOR_event_channel_op_compat which has been deprecated since
3.2.2 (i.e. long before Xen on ARM). Existing x86 code can still
safely and quietly using those calls, waiting for an unsuspecting ARM
porter to turn up and trip over it. This turns out to be rather
perplexing when it happens, since it can be obscured e.g. by various
conditionals like __XEN_INTERFACE_VERSION__ what is actually being
called.

Note that I'm making a distinction here between hypercalls which are
simply not used/implemented on arm (yet) and those which were
deprecated and replaced by a newer variant prior to Xen on ARM even
being invented.  The latter will never be implemented on ARM and have
non-deprecated aliases leading to confusion so those are the ones for
which a warning is useful.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Tested-by: Ard Biesheuvel <ard@linaro.org>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Julien Grall <julien.grall@citrix.com>