mmc: dw_mmc: remove the duplicated header file

<asm-generic/errno.h> is already included in <errno.h>.
It can use <errno.h> instead of <asm-generic/errno.h>

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mmc/exynos_dw_mmc.c b/drivers/mmc/exynos_dw_mmc.c
index 283befc..57271f1 100644
--- a/drivers/mmc/exynos_dw_mmc.c
+++ b/drivers/mmc/exynos_dw_mmc.c
@@ -10,12 +10,12 @@
 #include <fdtdec.h>
 #include <libfdt.h>
 #include <malloc.h>
+#include <errno.h>
 #include <asm/arch/dwmmc.h>
 #include <asm/arch/clk.h>
 #include <asm/arch/pinmux.h>
 #include <asm/arch/power.h>
 #include <asm/gpio.h>
-#include <asm-generic/errno.h>
 
 #define	DWMMC_MAX_CH_NUM		4
 #define	DWMMC_MAX_FREQ			52000000