clk: samsung: exynos5420: Add definition of clock ID for mout_sw_aclk_g3d

This patch adds ID for the mout_sw_aclk_g3d (SW_CLKMUX_ACLK_G3D) clock,
mostly for internal use in the CMU driver. It will allow to avoid the
__clk_lookup() call when setting up the clock during the clock provider
initialization.

Link: https://lore.kernel.org/r/20200811151251.31613-1-s.nawrocki@samsung.com


Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>