mmc: sdhci-msm: Fix recursive tuning issue

For any commands, that are sent during tuning sequence
CRC errors are expected. But if SDHCI_NEEDS_RETUNING flag
is set, then it will recursively do the tuning and gets
stuck in tuning. Fix this by not allowing the re-tuning to
happen while it is already in tuning process.

Change-Id: I9cc39f03a01c34f2f5639d4c20776fd575c25231
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>