media: v4l2-core: v4l2-i2c: convert to new API with ERRPTR

Use the new APIs instead of the deprecated ones.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

v4l2-core: fix coding style for the two new c files

As I2C and SPI parts of the V4L2 core got split, let's take
the chance and solve the CodingStyle issues there, as reported
by checkpatch --strict.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

media: v4l2-core: Remove BUG() from i2c and spi helpers

Currently, the i2c and spi subdev creation helpers
are calling BUG() when passed a NULL v4l2_device parameter.

This makes little sense; simply returning NULL seems more
sensible.

These two helpers may already return NULL on error, so callers
should already be checking for this, or at least be prepared
for a NULL result.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

media: v4l2-core: introduce a helper to unregister a i2c subdev

Introduce a new video4linux2 i2c helper, to unregister a subdev.
This allows to get rid of yet another ifdef.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: fix checkpatch warning]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

media: v4l2-core: move i2c helpers out of v4l2-common.c

Separate the i2c helpers to v4l2-i2c.c, in order to get rid
of the ifdefery. No functional changes intended, this is
just a cosmetic change to organize the code better.

Given I2C is a tristate symbol, a hidden boolean symbol
is introduced, to make the conditional build easier.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>