media: atomisp: don't check for ISP version for includes

As there aren't duplicated names anymore, and the end goal
is to do runtime checks between ISP2400 and ISP2401,
remove the part of the Makefile which changes the include
places based on the compile-time version.

This shouldn't cause any effect, but it will make easier
for further patches meant to remove conditional compiler
decisions between ISP versions to be replaced by
runtime ones.

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