ARM: dts: stm32: remove OV5640 pinctrl definition on stm32mp157c-ev1

"push-pull" configuration is now fully handled by the gpiolib and the
STMFX pinctrl driver. There is no longer need to declare a pinctrl group
to only configure "push-pull" setting for the line. It is done directly by
the gpiolib.

Fixes: a502b343 ("pinctrl: stmfx: update pinconf settings")
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>