mmc: tmio: hide unused tmio_mmc_clk_disable/tmio_mmc_clk_enable functions

When CONFIG_PM is disabled, we get a warning about the clock handling
being unused:

drivers/mmc/host/tmio_mmc_core.c:937:13: error: 'tmio_mmc_clk_disable' defined but not used [-Werror=unused-function]
 static void tmio_mmc_clk_disable(struct tmio_mmc_host *host)
             ^~~~~~~~~~~~~~~~~~~~
drivers/mmc/host/tmio_mmc_core.c:929:12: error: 'tmio_mmc_clk_enable' defined but not used [-Werror=unused-function]
 static int tmio_mmc_clk_enable(struct tmio_mmc_host *host)
            ^~~~~~~~~~~~~~~~~~~

As the clock handling is now done elsewhere, this is only used when
power management is enabled. We could make the functions as __maybe_unused,
but since there is already an #ifdef section, it seems easier to move
the helpers closer to their callers.

Fixes: b21fc294 ("mmc: tmio: move clk_enable/disable out of tmio_mmc_host_probe()")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>