ARM: dts: BCM5301X: Add TWD WD Support to DT

Add support for the ARM TWD Watchdog to the bcm5301x device tree.  The
ARM TWD timer allocated the register space for the WDT, so this patch
necessitated shrinking that.  Also, the GIC masks were added for these.

Signed-off-by: Jon Mason <jonmason@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>