imx6: move all standard includes to mx6_common.h

The linux/sizes.h, asm/arch/imx-regs.h, asm/imx-common/gpio.h,
config_cmd_default.h includes are used fairly universally across imx6 boards
so include them in mx6_common.h by default.

We define CONFIG_SYS_NO_FLASH before config_cmd_default.h  so that we
don't have to undef CONFIG_CMD_FLASH / CONFIG_CMD_IMLS everywhere.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
diff --git a/include/configs/mx6_common.h b/include/configs/mx6_common.h
index e0528ce..85bf039 100644
--- a/include/configs/mx6_common.h
+++ b/include/configs/mx6_common.h
@@ -31,4 +31,11 @@
 #define CONFIG_MP
 #define CONFIG_MXC_GPT_HCLK
 
+#define CONFIG_SYS_NO_FLASH
+
+#include <linux/sizes.h>
+#include <asm/arch/imx-regs.h>
+#include <asm/imx-common/gpio.h>
+#include <config_cmd_default.h>
+
 #endif