ARM: dts: i.MX51 babbage: Add spi-cs-high property to pmic

The mc13892 driver knows that it needs spi-cs-high, so the mc13892
will work. The dataflash also connected to this bus though can only
be probed when the mc13892 is inactive. Due to driver potential
differences in the probe order we can only make sure the mc13892
is inactive when we put the information into the devicetree.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>