MIPS: Watch: Avoid duplication of bits in mips_install_watch_registers.

MIPS: Watch: Avoid duplication of bits in mips_install_watch_registers.

Currently the bits to be set in the watchhi register in addition to that
requested by the user is defined inline for each register. To avoid
this, define the bits once and or that in for each register.

Signed-off-by: Matt Redfearn <matt.redfearn@mips.com>
Acked-by: David Daney <david.daney@cavium.com>
Reviewed-by: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/18157/
Signed-off-by: James Hogan <jhogan@kernel.org>