arm64: dts: arm: Fix SP805 clock-names

The SP805 binding sets the name for the actual watchdog clock to
"wdog_clk" (with an underscore).

Change the name in the DTs for ARM Ltd. platforms to match that. The
Linux and U-Boot driver use the *first* clock for this purpose anyway,
so it does not break anything.

Link: https://lore.kernel.org/r/20200828130602.42203-3-andre.przywara@arm.com


Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>