platform/x86/amd/hsmp: mark hsmp_msg_desc_table[] as maybe_unused

After the file got split, there are now W=1 warnings for users that
include it without referencing hsmp_msg_desc_table:

In file included from arch/x86/include/asm/amd_hsmp.h:6,
                 from drivers/platform/x86/amd/hsmp/plat.c:12:
arch/x86/include/uapi/asm/amd_hsmp.h:91:35: error: 'hsmp_msg_desc_table' defined but not used [-Werror=unused-const-variable=]
   91 | static const struct hsmp_msg_desc hsmp_msg_desc_table[] = {
      |                                   ^~~~~~~~~~~~~~~~~~~

Mark it as __attribute__((maybe_unused)) to shut up the warning but
keep it in the file in case it is used from userland. The __maybe_unused
shorthand unfortunately isn't available in userspace, so this has to
be the long form.

While it is not envisioned a normal userspace program could benefit
from having this table as part of UAPI, it seems there is non-zero
chance this array is used by some userspace tests so it is retained for
now (see the Link below).

Fixes: e47c018a ("platform/x86/amd/hsmp: Move platform device specific code to plat.c")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/platform-driver-x86/CAPhsuW7mDRswhVjYf+4iinO+sph_rQ1JykEof+apoiSOVwOXXQ@mail.gmail.com/
Link: https://lore.kernel.org/r/20241028163553.2452486-1-arnd@kernel.org


Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>