ARM: dts: imx53-qsb-common: fix FEC pinmux config

The pinmux configuration in device tree was different from manual
muxing in <u-boot>/board/freescale/mx53loco/mx53loco.c
All pins were configured as NO_PAD_CTL(1 << 31), which was fine as the
bootloader already did the correct pinmuxing for us.
But recently u-boot is migrating to reuse device tree files from the
kernel tree, so it seems to be better to have the correct pinmuxing in
our files, too.

Signed-off-by: Patrick Bruenn <p.bruenn@beckhoff.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>