arm: Don't include common.h in header files

It is bad practice to include common.h in other header files since it can
bring in any number of superfluous definitions. It implies that some C
files don't include it and thus may be missing CONFIG options that are set
up by that file. The C files should include these themselves.

Update some header files in arch/arm to drop this.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/spl.h

@@ -26,6 +26,8 @@ struct image_header;
 #define MMCSD_MODE_FS		2
 #define MMCSD_MODE_EMMCBOOT	3
 
+struct image_header;
+
 /*
  * u_boot_first_phase() - check if this is the first U-Boot phase
  *