mmc: core: Simplify by adding mmc_execute_tuning()

For each MMC, SD and SDIO there is code that
holds the clock, calls ops->execute_tuning, and
releases the clock. Simplify the code a bit by
providing a separate function to do that.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Git-commit: 63e415c64003fd62a302a1dc19f082e2c6f1b7cc
Git-repo: git://git.linaro.org/people/ulf.hansson/mmc.git


Change-Id: I0e5eb28ab2a34ea4d30628f5e607103166a46b9b
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>