ARM: ux500: disable msp2 node on Snowball

Analogous to commit 8858d88a25142544843869f0cd3e6654aa7b4aec
that fixed commit 70b41abc151f9
"ARM: ux500: move MSP pin control to the device tree"
accidentally activated MSP2, giving rise to a boot scroll
scream as the kernel attempts to probe a driver for it and
fails to obtain DMA channel 14.

For some reason I forgot to fix this on the Snowball. Fix
this up by marking the node disabled again.

Cc: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Kevin Hilman <khilman@linaro.org>