clk: mediatek: mt8516: Remove unused variable

Variable 'ddrphycfg_parents' is defined static and initialized, but not
used in the file.

../drivers/clk/mediatek/clk-mt8516.c:234:27: warning: ‘ddrphycfg_parents’ defined but not used [-Wunused-const-variable=]
 static const char * const ddrphycfg_parents[] __initconst = {
                           ^~~~~~~~~~~~~~~~~

Signed-off-by: Philippe Mazenauer <philippe.mazenauer@outlook.de>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>