MIPS: BCM63XX: fix switch core reset on BCM6368

The Ethernet Switch core mask was set to 0, causing the switch core to
be not reset on BCM6368 on boot. Provide the proper mask so the switch
core gets reset to a known good state.

Fixes: 799faa62 ("MIPS: BCM63XX: add core reset helper")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>