clk: rzg2l: Ignore enable for core clocks

clk: rzg2l: Ignore enable for core clocks

In the RZ/G2L family, core clocks are always on and can't be disabled.
However, drivers which are shared with other SoCs may call clk_enable()
or clk_enable_bulk() for a clock referenced in the device tree which
happens to be a core clock on the RZ/G2L. To avoid the need for
conditionals in these drivers, simply ignore attempts to enable a core
clock.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>