A NO_PAD_CTRL flag used to keep a pad configuration untouched.
With commit 094820a63bfd ("i.MX: iomuxv3: Use helper functions in iomux-v3.h")
the NO_PAD_CTRL semantic changed to set a pad configurations to zero, which
breaks non-DT boards, where NO_PAD_CTRL is freqently used to keep a boot-up
default pad configuration, which often is non zero.

Restore the old semantic, dont write PAD_CTRL when NO_PAD_CTRL is set.

Signed-off-by: Alexander Kurz <akurz@blala.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>