Commit 373e6a (mmc: sdhci: R1B command handling + MMC_CAP_ERASE) moved the
handling of SDHCI_QUIRK_TIMEOUT_USES_SDCLK from sdhci_calc_timeout() to
sdhci_add_host(). This causes division by zero errors on at least the S3C
SDHCI controller as the quirk implementation needs host->clock set to work
but host->clock has not been set when sdhci_add_host() is called.

Fix this by backing out that portion of the change, the clock may vary at
runtime anyway. It does occur to me that we may want to move the quirk to
where we set the clock but this seems more invasive and I'm concerned
about undesirable side effects.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Andrei Warkentin <andreiw@motorola.com>
Signed-off-by: Chris Ball <cjb@laptop.org>