[media] am437x-vfpe: fix typo in vpfe_get_app_input_index

gcc-6 points out an obviously silly comparison in vpfe_get_app_input_index():

drivers/media/platform/am437x/am437x-vpfe.c: In function 'vpfe_get_app_input_index':
drivers/media/platform/am437x/am437x-vpfe.c:1709:27: warning: self-comparison always evaluats to true [-Wtautological-compare]
       client->adapter->nr == client->adapter->nr) {
                           ^~

This was introduced in a slighly incorrect conversion, and it's
clear that the comparison was meant to compare the iterator
to the current subdev instead, as we do in the line above.

Fixes: d3723239 ("[media] media: am437x-vpfe: match the OF node/i2c addr instead of name")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>