Some devices enumerate various clocks in their DT, and many drivers
just blanketly try to enable all of them. This creates problems
since we only model a few gate clocks, and the clock driver outputs
a warning when a clock is not described:
=========
sunxi_set_gate: (CLK#3) unhandled
=========

Some clocks don't have an enable bit, or are already enabled in a
different way, so we might want to just ignore them.

Add a CCU_CLK_F_DUMMY_GATE flag that indicates that case, and define
a GATE_DUMMY macro that can be used in the clock description array.
Define a few clocks, used by some pinctrl devices, that way to suppress
the runtime warnings.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Reviewed-by: NSamuel Holland <samuel@sholland.org>