ARM: S5P64X0: Remove unused variable in dma.c file

Fixes the following warning:
arch/arm/mach-s5p64x0/dma.c:39:12: warning: 'dma_dmamask' defined but not used
[-Wunused-variable]
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NKukjin Kim <kgene.kim@samsung.com>

arch/arm/mach-s5p64x0/dma.c

@@ -36,8 +36,6 @@
 #include <plat/devs.h>
 #include <plat/irqs.h>
 
-static u64 dma_dmamask = DMA_BIT_MASK(32);
-
 static u8 s5p6440_pdma_peri[] = {
 	DMACH_UART0_RX,
 	DMACH_UART0_TX,