MIPS: Alchemy: Touchscreen support on DB1100

Wire up the ADS7846 touchscreen controller on the DB1100.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2879/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>