MIPS: BCM63XX: add clkdev lookup support

Enable clkdev lookup support to allow us providing clocks under
different names to devices more easily, so we don't need to care
about clock name clashes anymore.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: linux-mips@linux-mips.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-serial@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: bcm-kernel-feedback-list@broadcom.com
Patchwork: https://patchwork.linux-mips.org/patch/17325/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: James Hogan <jhogan@kernel.org>