ARM: u300: delete custom pin hog code

With recent changes in the kernel, the MMCI and PL011 UART
drivers will autonomously request their pins to be muxed in,
so this machine-specific pin hogging code is just interfering
with the proper mechanism and causing regressions in the v3.8
kernel. Delete it and the problems go away.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>