mmc: sh_mmcif: remove some cruft

The TODO section from 2010 is obsolete. We have DMA and PM meanwhile and
we always want to handle errors better, if possible. Also DRIVER_VERSION
is not used anymore these days.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>