ARM: EXYNOS: fix build error when MFC is not selected

This fixes following:
arch/arm/mach-exynos/built-in.o: In function `exynos5_reserve':
arch/arm/mach-exynos/mach-exynos5-dt.c:177: undefined reference to `s5p_fdt_find_mfc_mem'
arch/arm/mach-exynos/mach-exynos5-dt.c:177: undefined reference to `s5p_fdt_find_mfc_mem'
arch/arm/mach-exynos/mach-exynos5-dt.c:178: undefined reference to `s5p_mfc_reserve_mem'

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/mach-exynos/mach-exynos5-dt.c

@@ -163,13 +163,15 @@ static char const *exynos5_dt_compat[] __initdata = {
 
 static void __init exynos5_reserve(void)
 {
+#ifdef CONFIG_S5P_DEV_MFC
 	struct s5p_mfc_dt_meminfo mfc_mem;
 
 	/* Reserve memory for MFC only if it's available */
 	mfc_mem.compatible = "samsung,mfc-v6";
 	if (of_scan_flat_dt(s5p_fdt_find_mfc_mem, &mfc_mem))
 		s5p_mfc_reserve_mem(mfc_mem.roff, mfc_mem.rsize, mfc_mem.loff,
 				mfc_mem.lsize);
+#endif
 }
 
 DT_MACHINE_START(EXYNOS5_DT, "SAMSUNG EXYNOS5 (Flattened Device Tree)")