[media] drx-j: Be sure that all allocated data are properly initialized

The state struct is allocated without cleaning the memory.
This causes random bugs.

Clean it, and move the memcpy functions just below each kalloc,
to be clearer that all those data are properly filled.

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