mmc: remove tmio_mmc driver

With the TMIO MFD support gone, the corresponding MMC host driver can
be removed as well. The remaining tmio_mmc_core module however is still
used by both the Renesas and Socionext host drivers.

Cc: Ian Molton <spyro@f2s.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: linux-mmc@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>