mmc: tmio: always get number of taps

Current code gets number of taps only once and keeps the value. This is
not correct, we need to obtain it every time before executing tuning,
so remove the outer if-block.

Signed-off-by: Masaharu Hayakawa <masaharu.hayakawa.ry@renesas.com>
[wsa: extracted from a larger patch and reworded commit message]
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>