mmc: sdhci-msm: Always set max_busy_timeout as zero

Qcom SDHC uses base clock in calculating the data-timeout
value. So SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK quirk is set.

Moreover discard size calculation uses max_busy_timeout in deriving the
value. So, we can ensure a larger discard size by setting this
timeout as zero. If this timeout is zero then it takes max erase
timeout vlaue (which is 60sec) in the discard size calculation.

But when this quirk is set max_busy_timeout variable gets updated
to non zero value leading to smaller discard size.

Define get_max_timeout_count ops in sdhci_msm_ops which always sets
max_busy_timeout to zero.

Change-Id: Iec6013dde6082b2a8fdb449cacf503c290252d0b
Signed-off-by: Sarthak Garg <sartgarg@codeaurora.org>