powerpc/85xx: bsc9131 - Correct typo in SDHC device node

BSC9131RDB doesn't have SDHC enabled. As a result of this typo,
the node was not getting disabled from the device tree which was
leading to linux hang during bootup

Signed-off-by: Harninder Rai <harninder.rai@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>