mmc: tmio: use BIT() within defines

BIT() makes it easier to match the bits to the datasheet. This is
especially important here, since some variants have different names in
their datasheets (like with Renesas R-Car).

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