crypto: caam: Avoid unused imx8m_machine_match variable

crypto: caam: Avoid unused imx8m_machine_match variable

If caam module is built without OF support, the compiler returns the
following warning:

	drivers/crypto/caam/ctrl.c:83:34: warning: 'imx8m_machine_match' defined but not used [-Wunused-const-variable=]

imx8m_machine_match is only referenced by of_match_node(), which is set
to NULL if CONFIG_OF is not set, as of commit 5762c20593b6b ("dt: Add
empty of_match_node() macro"):

	#define of_match_node(_matches, _node)  NULL

Do not create imx8m_machine_match if CONFIG_OF is not set.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407011309.cpTuOGdg-lkp@intel.com/
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20240702185557.3699991-2-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>