ARM: dts: sunxi: Explicitly enable pull-ups for MMC pins

In the past, all the MMC pins had

	allwinner,pull = <SUN4I_PINCTRL_NO_PULL>;

which was actually a no-op. We were relying on U-boot to set the bias
pull up for us. These properties were removed as part of the fix up to
actually support no bias on the pins. During the transition some boards
experienced regular MMC time-outs during normal operation, while others
completely failed to initialize the SD card.

Given that MMC starts in open-drain mode and the pull-ups are required,
it's best to enable it for all the pin settings.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>