media: dt-bindings: dw9714, dw9807-vcm: Add files to MAINTAINERS, rename files

Add the DT binding documentation for dw9714 and dw9807-vcm to the
MAINTAINERS file. The dw9807-vcm binding documentation file is renamed to
match the dw9807's VCM bit's compatible string.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>