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>
1 file changed