mmc: sdhci: Always pass clock request value zero to set_clock host op

To allow the set_clock host op to disable the SDCLK source when not
needed, always call the host op when the requested clock speed is
zero.  Do this even if host->clock already equals zero, because
the SDHCI driver may set that value (without calling the host op)
to force an update at the next (non-zero-speed) call.
Signed-off-by: NTodd Poynor <toddpoynor@google.com>
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Signed-off-by: NChris Ball <cjb@laptop.org>

drivers/mmc/host/sdhci.c

@@ -1068,7 +1068,7 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
 	u16 clk = 0;
 	unsigned long timeout;
 
-	if (clock == host->clock)
+	if (clock && clock == host->clock)
 		return;
 
 	host->mmc->actual_clock = 0;