Refactor the camerarx start and stop procedure to group all the
corresponding operations in two functions, cal_camerarx_start() and
cal_camerarx_stop() instead of splitting them in multiple steps called
from the vb2 stream start and stop functions. This reduces the coupling
between the camerarx and the contexts, and better models the camerarx
hardware.

The cal_camerarx_start() is a reworked version of cal_camerarx_init()
with the description of the start procedure updated to match the AM65x,
DRA7[124567]x and DRA80xM TRMs. The cal_camerarx_wait_ready() function
is inlined in cal_camerarx_start() to better describe the start
procedure.

No functional change is included in the camerarx start and stop
procedures themselves, but the interleaving of the start steps with the
context configuration has been changed in cal_start_streaming().
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>