MIPS: GIC: Fix GICBIS macro

MIPS: GIC: Fix GICBIS macro

The GICBIS macro could update the GIC registers incorrectly, depending
on the data value passed in:

* Bits were only OR'd into the register data, so register fields could
  not be cleared.

* Bits were OR'd into the register data without masking the data to the
  correct field width, corrupting adjacent bits.

Signed-off-by: Jeffrey Deans <jeffrey.deans@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7378/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>