media: atomisp: Add ia_css_frame_get_info() helper

Several places rely on the [frame_]info member being the first member of
struct ia_css_frame, so that &frame->info will yield NULL when frame is
NULL (some places already explicitly check for a NULL frame pointer but
not nearly all).

For videobuf2 support the vb2_v4l2_buffer struct needs to be embedded
in the frame struct and it needs to be the first member. Breaking the
assumption that &frame->info will yield NULL when frame is NULL.

Add a ia_css_frame_get_info() helper to return either the ia_css_frame_info
struct embedded in the frame, or NULL when the frame pointer is NULL and
use this in places where a ia_css_frame_info ptr or NULL is expected.

To make sure that we catch all uses of the info field this patch also
renames the info field to frame_info.

This is a preparation patch for converting the driver to videobuf2.

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>