sdhci: be more strict with get_min_clock() usage

get_min_clock() makes sense only with NONSTANDARD_CLOCK quirk and when
set_clock() callback is specified.

The patch should cause no functional changes, it just makes the code
self-documented and avoids any possible misuse of get_min_clock().
Suggested-by: NPierre Ossman <pierre@ossman.eu>
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Cc: Ian Molton <ian@mnementh.co.uk>
Cc: Matt Fleming <matt@console-pimps.org>
Cc: Philip Langdale <philipl@overt.org>
Cc: Pierre Ossman <pierre@ossman.eu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/sdhci.c

@@ -1772,7 +1772,8 @@ int sdhci_add_host(struct sdhci_host *host)
 	 * Set host parameters.
 	 */
 	mmc->ops = &sdhci_ops;
-	if (host->ops->get_min_clock)
+	if (host->quirks & SDHCI_QUIRK_NONSTANDARD_CLOCK &&
+			host->ops->set_clock && host->ops->get_min_clock)
 		mmc->f_min = host->ops->get_min_clock(host);
 	else
 		mmc->f_min = host->max_clk / 256;