arm: spear6xx: remove unneeded pinctrl properties in spear600-evb

The spear6xx doesn't have a pinctrl driver, since the pinmux is globally
defined through a single register, generally configured by the
firmware/bootloader.

Therefore, the pinctrl related properties in spear600-evb.dts are not
necessary.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>