clk: ingenic: Mark ingenic_tcu_of_match as __maybe_unused

clk: ingenic: Mark ingenic_tcu_of_match as __maybe_unused

This device id table is passed to of_match_node() later on in probe, but
on CONFIG_OF=n builds of_match_node() doesn't do anything with the
arguments. Lets just mark the table unused so that the compiler doesn't
complain about this.

drivers/clk/ingenic/tcu.c:326:34: warning: unused variable 'ingenic_tcu_of_match' [-Wunused-const-variable]
static const struct of_device_id ingenic_tcu_of_match[] __initconst = {
^
1 warning generated.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20200528233837.70269-1-sboyd@kernel.org