mmc: renesas_sdhi: Fix sampling clock position selecting

When tuning each tap is issued CMD19 twice and the result of both runs
recorded in host->taps. If the result is different between the two runs
the wrong sampling clock position was selected. Fix this by merging the
two runs and only keep the result for each tap if it was good in both
sets.

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