mach-u1: Unmap HOME key GPIO on SGH-I777

This device doesn't have a HOME key - Having the GPIO
mapped and floating with no input leads to spurious
HOME key presses detected.

Signed-off-by: Andrew Dodd <atd7@cornell.edu>

Conflicts:

	arch/arm/mach-exynos/mach-u1.c

Change-Id: I4169258e66acd4596768868432b7cce8b3066554