media: atomisp: Add input helper variable for isp->asd->inputs[asd->input_curr]

Passing 'isp->asd->inputs[asd->input_curr].foo' as argument to
various function calls is rather long.

Add a local input helper variable for this, so that the function
calls will fit on one line.

Link: https://lore.kernel.org/r/20230529103741.11904-13-hdegoede@redhat.com



Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>