mmc: meson-gx: remove unneeded devm_kstrdup in meson_mmc_clk_init

CLK core does a deep copy of init.name, therefore it's fully ok to
provide a local variable.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>