media: atomisp: Remove remaining deferred firmware loading code

media: atomisp: Remove remaining deferred firmware loading code

There is a bunch of dead code left from the deferred firmware loading
support which was removed in commit 8972ed6ea7a0 ("media: atomisp: Remove
deferred firmware loading support").

Remove this dead code:
- Remove the skip_fwload module parameter
- Remove the now always NULL fw argument from ia_css_init()
- Remove the fw_explicitly_loaded boolean from sh_css.c
  (this was always true now)
- Adjust some function kernel-doc comments to match

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