mmc: host: fix depends for MMC_MESON_GX w/ COMPILE_TEST

mmc: host: fix depends for MMC_MESON_GX w/ COMPILE_TEST

Fix build errors for meson-gx-mmc.c when CONFIG_COMMON_CLK is not
set/enabled. This can happen when COMPILE_TEST is set/enabled.

ERROR: modpost: "clk_divider_ops" [drivers/mmc/host/meson-gx-mmc.ko] undefined!
ERROR: modpost: "devm_clk_register" [drivers/mmc/host/meson-gx-mmc.ko] undefined!
ERROR: modpost: "clk_mux_ops" [drivers/mmc/host/meson-gx-mmc.ko] undefined!
ERROR: modpost: "__clk_get_name" [drivers/mmc/host/meson-gx-mmc.ko] undefined!

Fixes: b7425e432fa3 ("mmc: host: Enable compile testing of multiple drivers")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/20200925164323.29843-1-rdunlap@infradead.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>