media: atomisp: Remove deferred firmware loading support

Make atomisp behave like any other drivers and have it load the firmware
at probe time (as it was already doing by default).

The deferred firmware loading support needlessly complicates the
v4l2_file_operations.open callback (atomisp_open()), getting in
the way of allowing multiple opens like a normal v4l2 device would.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>