MIPS: pci: Make use of the BIT() macro inside the mt7620 driver

There are a few defines that manully shift a bit. Change these to using
the BIT() macro.

Signed-off-by: John Crispin <john@phrozen.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15322/


Signed-off-by: James Hogan <jhogan@kernel.org>