altera_spi: add spi_set_speed

Added this for mmc_spi driver. Though altera spi core does not
support programmable speed. It is fixed when configured in
sopc-builder.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Signed-off-by: Scott McNutt <smcnutt@psyent.com>

drivers/spi/altera_spi.c

@@ -70,6 +70,11 @@ void spi_init(void)
 {
 }
 
+void spi_set_speed(struct spi_slave *slave, uint hz)
+{
+	/* altera spi core does not support programmable speed */
+}
+
 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 				  unsigned int max_hz, unsigned int mode)
 {