watchdog: pic32-dmt: Add PIC32 deadman timer driver

Adds support for the deadman timer peripheral found on PIC32 class devices.

The primary function of the deadman timer (DMT) is to reset the processor
in the event of a software malfunction. The DMT is a free-running
instruction fetch timer, which is clocked whenever an instruction fetch
occurs until a count match occurs. Instructions are not fetched when
the processor is in sleep mode.

Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Signed-off-by: Joshua Henderson <joshua.henderson@microchip.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-watchdog@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12703/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>