mmc: core: make erase timeout calculation allow for gated clock

The erase timeout calculation may depend on clock rate
which is zero if the clock is gated, so use
mmc_host_clk_rate() which allows for that case.
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Signed-off-by: NChris Ball <cjb@laptop.org>

drivers/mmc/core/core.c

@@ -1245,7 +1245,7 @@ static unsigned int mmc_mmc_erase_timeout(struct mmc_card *card,
 		 */
 		timeout_clks <<= 1;
 		timeout_us += (timeout_clks * 1000) /
-			      (card->host->ios.clock / 1000);
+			      (mmc_host_clk_rate(card->host) / 1000);
 
 		erase_timeout = timeout_us / 1000;