renesas: Renesas R-Car Gen4 watchdog driver

renesas: Renesas R-Car Gen4 watchdog driver

Add support of Renesas R-Car Gen4 watchdog timer. Timeouts up to
8184.0s are supported (CKS1 register is not involved). The watchdog
uses the clock of type CLK_TYPE_GEN4_MDSEL.

The timeout is set in
dts/upstream/src/arm64/renesas/r8a779f0-spider-cpu.dtsi section &rwdt.

This driver is based on upstream linux commit:
e70140ba0d2b("Get rid of 'remove_new' relic from platform driver struct")

Signed-off-by: Shmuel Leib Melamud <smelamud@redhat.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>