tools: kwbimage: Do not cast const pointers to non-const pointers

Avoid casting const to non-const.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/tools/kwbimage.h b/tools/kwbimage.h
index 8d37357..c000cba 100644
--- a/tools/kwbimage.h
+++ b/tools/kwbimage.h
@@ -235,11 +235,11 @@
 {
 	uint32_t ohdr_size;
 
-	if ((void *)(ohdr + 1) > mhdr_end)
+	if ((const void *)(ohdr + 1) > mhdr_end)
 		return 0;
 
 	ohdr_size = opt_hdr_v1_size(ohdr);
-	if (ohdr_size < 8 || (void *)((uint8_t *)ohdr + ohdr_size) > mhdr_end)
+	if (ohdr_size < 8 || (const void *)((const uint8_t *)ohdr + ohdr_size) > mhdr_end)
 		return 0;
 
 	return 1;