media: atomisp: make dfs_config_merr_117a struct const

This setting is used only for one of te Merryfield PCI IDs.

As this is an ISP2400, we can just get rid of a version
test, writing the right value directly inside the struct.

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