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.

Change-Id: If99230d76138679b5767f77cb925f15408ae518e
Signed-off-by: Todd Poynor <toddpoynor@google.com>
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 58d5436..7fc5848 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1044,7 +1044,7 @@
 	u16 clk = 0;
 	unsigned long timeout;
 
-	if (clock == host->clock)
+	if (clock && clock == host->clock)
 		return;
 
 	if (host->ops->set_clock) {