i.MX6: add enable_spi_clk()

add enable_spi_clk(), so board code can enable spi clocks.

Signed-off-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Cc: Eric Nelson <eric.nelson@boundarydevices.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/include/asm/arch-mx6/imx-regs.h b/arch/arm/include/asm/arch-mx6/imx-regs.h
index 6c0a0d9..437b434 100644
--- a/arch/arm/include/asm/arch-mx6/imx-regs.h
+++ b/arch/arm/include/asm/arch-mx6/imx-regs.h
@@ -505,6 +505,7 @@
 #define MXC_CSPICTRL_RXOVF	(1 << 6)
 #define MXC_CSPIPERIOD_32KHZ	(1 << 15)
 #define MAX_SPI_BYTES	32
+#define SPI_MAX_NUM	4
 
 /* Bit position inside CTRL register to be associated with SS */
 #define MXC_CSPICTRL_CHAN	18