Fix compilation warning on MSVC
MSVC complains about the negation in `(uint32_t) -1u`. This commit fixes this by
using `(uint32_t) -1` instead.
@@ -471,7 +471,7 @@ int mbedtls_net_poll( mbedtls_net_context *ctx, uint32_t rw, uint32_t timeout )
tv.tv_usec = ( timeout % 1000 ) * 1000;
ret = select( fd + 1, &read_fds, &write_fds, NULL,
- timeout == (uint32_t) -1u ? NULL : &tv );
+ timeout == (uint32_t) -1 ? NULL : &tv );
if( ret < 0 )
return( MBEDTLS_ERR_NET_POLL_FAILED );
