spi: kirkwood_spi.c: Make global variable static

Signed-off-by: Stefan Roese <sr@denx.de>
Acked-by: Prafulla Wadaskar <prafulla@marvell.com>
Tested-by: Luka Perkov <luka@openwrt.org>
Reviewed-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>

drivers/spi/kirkwood_spi.c

@@ -18,7 +18,7 @@
 
 static struct kwspi_registers *spireg = (struct kwspi_registers *)KW_SPI_BASE;
 
-u32 cs_spi_mpp_back[2];
+static u32 cs_spi_mpp_back[2];
 
 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 				unsigned int max_hz, unsigned int mode)