ARM: ux500: drop STM pinmap settings

The pin mappings for the STM (System Trace Macrocell) are not
really used by anything: we have no driver for is and the settings
are not connected to any device. We can recreate the different
mux outputs in the device tree the day we need them. Drop these
for now.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>