media: atomisp: fix bad usage at error handling logic

As warned by sparse:
	atomisp: drivers/staging/media/atomisp/pci/atomisp_acc.c:508 atomisp_acc_load_extensions() warn: iterator used outside loop: 'acc_fw'

The acc_fw interactor is used outside the loop, at the error handling
logic. On most cases, this is actually safe there, but, if
atomisp_css_set_acc_parameters() has an error, an attempt to use it
will pick an invalid value for acc_fw.

Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>