[U-Boot] [PATCH 2/4 v3] spi: add spi_set_speed func

[Thomas Chou]

This func helps mmc_spi driver set correct speed for mmc/sd, as
mmc card needs 400KHz clock for spi mode initialization.

Signed-off-by: Thomas Chou <thomas at wytron.com.tw>
---
v2 remove weak func as Mike suggested.
v3 comment style fix as Wolfgang suggested.

 include/spi.h |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/include/spi.h b/include/spi.h
index 320e50e..e364d2d 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -175,6 +175,14 @@ void spi_cs_activate(struct spi_slave *slave);
  */
 void spi_cs_deactivate(struct spi_slave *slave);
 
+/*
+ * Set transfer speed.
+ * This sets a new speed to be applied for next spi_xfer().
+ *   slave:	The SPI slave
+ *   hz:	The transfer speed
+ */
+void spi_set_speed(struct spi_slave *slave, uint hz);
+
 /*-----------------------------------------------------------------------
  * Write 8 bits, then read 8 bits.
  *   slave:	The SPI slave we're communicating with
-- 
1.7.3.4