Add explicit unsigned-to-signed integer conversion
The previous code triggered a compiler warning because of a comparison
of a signed and an unsigned integer.
The conversion is safe because `len` is representable by 16-bits,
hence smaller than the maximum integer.
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 2be66ef..0c3f1a8 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -1893,7 +1893,7 @@
len = (*p)[0] << 8 | (*p)[1];
*p += 2;
- if( end - (*p) < len )
+ if( end - (*p) < (int) len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad server key exchange message "
"(psk_identity_hint length)" ) );