clk: renesas: Handle CLK_TYPE_GEN4_MDSEL in gen3_clk_get_rate64()

clk: renesas: Handle CLK_TYPE_GEN4_MDSEL in gen3_clk_get_rate64()

Add support of CLK_TYPE_GEN4_MDSEL clock type to gen3_clk_get_rate64()
function. In particular, this type of clock is used by Renesas R-Car
Gen4 watchdog. It operates similarly to CLK_TYPE_GEN3_MDSEL clock.

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