mtd: omap2: fix static declaration warning

This patch fixes sparse warning for static declaration of variable "use_dma"

drivers/mtd/nand/omap2.c:114:11: warning: symbol 'use_dma' was not declared. Should it be static?
Signed-off-by: NG, Manjunath Kondaiah <manjugk@ti.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/omap2.c

@@ -111,11 +111,11 @@ static int use_dma = 1;
 module_param(use_dma, bool, 0);
 MODULE_PARM_DESC(use_dma, "enable/disable use of DMA");
 #else
-const int use_dma;
+static const int use_dma;
 #endif
 #else
 const int use_prefetch;
-const int use_dma;
+static const int use_dma;
 #endif
 
 struct omap_nand_info {