libnvdimm: mark 'security_show' static again

libnvdimm: mark 'security_show' static again

The security_show() function was made global and __weak at some
point to allow overriding it. The override was removed later, but
it remains global, which causes a warning about the missing
declaration:

drivers/nvdimm/dimm_devs.c:352:9: error: no previous prototype for 'security_show'

This is also not an appropriate name for a global symbol in the
kernel, so just make it static again.

Fixes: 15a8348707ff ("libnvdimm: Introduce CONFIG_NVDIMM_SECURITY_TEST flag")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20230516201415.556858-3-arnd@kernel.org
Signed-off-by: Dan Williams <dan.j.williams@intel.com>