armv7: Prevent CBFS data overlapping bootblock.

For arm/snow, current bootblock is larger than previously assigned CBFS offset
and will fail to boot. To prevent this happening again in future, cbfstool now
checks if CBFS will overlap bootblock.

A sample error message:
	E: Bootblock (0x0+0x71d4) overlap CBFS data (0x5000)
	E: Failed to create build/coreboot.pre1.tmp.

arm/snow offset is also enlarged and moved to Kconfig variable.

Change-Id: I4556aef27ff716556040312ae8ccb78078abc82d
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: http://review.coreboot.org/2295
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>

util/cbfstool/cbfs_image.c

@@ -174,6 +174,12 @@ int cbfs_image_create(struct cbfs_image *image,
 		      bootblock_offset, bootblock->size, size);
 		return -1;
 	}
+	if (entries_offset > bootblock_offset &&
+	    entries_offset < bootblock->size) {
+		ERROR("Bootblock (0x%x+0x%zx) overlap CBFS data (0x%x)\n",
+		      bootblock_offset, bootblock->size, entries_offset);
+		return -1;
+	}
 	memcpy(image->buffer.data + bootblock_offset, bootblock->data,
 	       bootblock->size);