media: v4l2-core: Module re-organization

videodev.ko and v4l2-common.ko driver are built under
the same conditions. Therefore, it doesn't make much sense
to split them in two different modules.

Splitting v4l2-common to its own driver was done many years ago:

  commit a9254475
  Author: Mauro Carvalho Chehab <mchehab@infradead.org>
  Date:   Tue Jan 29 18:32:35 2008 -0300

      V4L/DVB (7115): Fix bug #9833: regression when compiling V4L without I2C

Back then, the subsystem organization was different and the module split
was needed. However, with the current organization, there is no issue
compiling V4L2 with I2C as y/m/n.

This commit makes v4l2-common part of our V4L2 core driver (videodev.ko).

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>