tools, rsa: Further minor cleanups on top of c236ebd and 2b9ec7

[NOTE: I took v1 of these patches in, and then v2 came out, this commit
is squashing the minor deltas from v1 -> v2 of updates to c236ebd and
2b9ec76 into this commit - trini]

- Added an additional NULL check, as suggested by Simon Glass to
  fit_image_process_sig
- Re-formatted the comment blocks

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Simon Glass <sjg@chromium.org>
[For merging the chnages from v2 back onto v1]
Signed-off-by: Tom Rini <trini@konsulko.com>

lib/rsa/rsa-sign.c

@@ -420,8 +420,10 @@ static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
 		BN_rshift(num, num, 32); /*  N = N/B */
 	}
 
-	/* We try signing with successively increasing size values, so this
-	 * might fail several times */
+	/*
+	 * We try signing with successively increasing size values, so this
+	 * might fail several times
+	 */
 	ret = fdt_setprop(blob, noffset, prop_name, buf, size);
 	if (ret)
 		return -FDT_ERR_NOSPACE;