media: atomisp-ov2680: Fix ov2680_set_fmt() clobbering the exposure

Now that we restore the default or last user set exposure setting on
power_up() there is no need for the registers written by ov2680_set_fmt()
to write to the exposure register.

Not doing so fixes the exposure always being reset to the value from
the res->regs array after a set_fmt().

Link: https://lore.kernel.org/linux-media/20211107171549.267583-11-hdegoede@redhat.com


Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>