mmc: tmio: Keep generating clock when clock are enabled

mmc: tmio: Keep generating clock when clock are enabled

The TMIO core has a feature where it can automatically disable clock output
when the bus is not in use. While this is useful, it also interferes with
switching the bus to 1.8V and other background tasks of the SD/MMC cards,
which require clock to be enabled.

This patch respects the mmc->clk_disable and only disables the clock when
the MMC core requests it. Otherwise the clock are continuously generated
on the bus.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>