The ref_module() function is used for internal housekeeping of the
module code, it's not normally used by subsystems or device drivers,
and the use of ref_module in the omap_ssi_port driver causes a link
build error when modules are disabled:

hsi/controllers/omap_ssi_port.c: In function 'ssi_port_probe':
hsi/controllers/omap_ssi_port.c:1119:2: error: implicit declaration of function 'ref_module' [-Werror=implicit-function-declaration]

This changes the omap_ssi_port driver to use try_module_get()
and module_put() instead, which is the normal way to ensure that
the driver providing a device used in another module does not
go away.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Carlos Chinea <carlos.chinea@nokia.com>
Cc: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>