[media] drx-j: get rid of drx_driver.c

This file contains just the firmware load code, that it is also
somewhat duplicated at drxj.c.

Move the code into there. Latter patches will remove the
duplicated code.

Acked-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>