MIPS: Lantiq: Fix mask of GPE frequency

MIPS: Lantiq: Fix mask of GPE frequency

The hardware documentation says bit 11:10 are used for the GPE
frequency selection. Fix the mask in the define to match these bits.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Thomas Langer <thomas.langer@intel.com>
Cc: linux-mips@linux-mips.org
Cc: john@phrozen.org
Patchwork: https://patchwork.linux-mips.org/patch/14648/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>