[media] coda: move BIT processor command execution out of pic_run_work

In preparation for the split, move the AXI_SRAM_USE register access and the
PIC_RUN command execution out of pic_run_work into prepare_encode/decode.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>