tools: kwboot: Fix return type of kwboot_xm_makeblock() function

Function kwboot_xm_makeblock() always returns length of xmodem block. It
is always non-negative and calculated from variable with size_t type. Set
return type of this function to size_t and remove dead code which checks
for negative value.

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/kwboot.c b/tools/kwboot.c
index b9a402c..88353d1 100644
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -347,7 +347,7 @@
 	return rc;
 }
 
-static int
+static size_t
 kwboot_xm_makeblock(struct kwboot_block *block, const void *data,
 		    size_t size, int pnum)
 {
@@ -441,9 +441,6 @@
 		n = kwboot_xm_makeblock(&block,
 					data + N, size - N,
 					pnum++);
-		if (n < 0)
-			goto can;
-
 		if (!n)
 			break;