media: atomisp: get rid of spmem_dump.c

Those files seem to be firmware-dependent, probably being used
by some debug interface.

Well, their contents are not really used by atomisp, so let's
just send them to the trash can, as it shouldn't have any
usage upstream.

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