[media] st-cec: Fix module autoload

[media] st-cec: Fix module autoload

If the driver is built as a module, autoload won't work because the module
alias information is not filled. So user-space can't match the registered
device with the corresponding module.

Export the module alias information using the MODULE_DEVICE_TABLE() macro.

Before this patch:

$ modinfo drivers/staging/media//st-cec/stih-cec.ko | grep alias
$

After this patch:

$ modinfo drivers/staging/media//st-cec/stih-cec.ko | grep alias
alias:          of:N*T*Cst,stih-cecC*
alias:          of:N*T*Cst,stih-cec

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>