ARM: dts: meson8b: odroidc1: add the GPIO line names

This adds the GPIO line names from the schematics to get them displayed
in the debugfs output of each GPIO controller.

The schematics from Odroid-C1+ PCB revision 0.4 20150615 are used as
referenced.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>