media: atomisp: remove some file duplication and do more dir renames

There are currently two identical copies of some files, one
at css_2401_csi2p_system/ and another one at css_2401_system/.

Get rid of one of them, moving the remaining files to the
directory with the shortest name.

While here, do more renames, in order to get smaller path
names.

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