omap3_spi: receive transmit mode

Implementation of receive-transmit mode for
omap3 MCSPI.

Introduces full duplex communication, needed by
some spi devices (such as enc28j60).

Signed-off-by: jacopo mondi <mondi@cs.unibo.it> <j.mondi@voltaelectronics.com>
diff --git a/drivers/spi/omap3_spi.h b/drivers/spi/omap3_spi.h
index b8e3a4c..0ac801c 100644
--- a/drivers/spi/omap3_spi.h
+++ b/drivers/spi/omap3_spi.h
@@ -109,6 +109,8 @@
 	return container_of(slave, struct omap3_spi_slave, slave);
 }
 
+int omap3_spi_txrx(struct spi_slave *slave, unsigned int len, const u8 *txp,
+			u8 *rxp, unsigned long flags);
 int omap3_spi_write(struct spi_slave *slave, unsigned int len, const u8 *txp,
 		    unsigned long flags);
 int omap3_spi_read(struct spi_slave *slave, unsigned int len, u8 *rxp,