net/mlx5e: Initialize on stack link modes bitmap

Initialize link modes bitmap on stack before using it, otherwise the
outcome of ethtool set link ksettings might have unexpected values.

Fixes: 4b95840a ("net/mlx5e: Fix matching of speed to PRM link modes")
Signed-off-by: Aya Levin <ayal@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c

@@ -1021,7 +1021,7 @@ static bool ext_link_mode_requested(const unsigned long *adver)
 {
 #define MLX5E_MIN_PTYS_EXT_LINK_MODE_BIT ETHTOOL_LINK_MODE_50000baseKR_Full_BIT
 	int size = __ETHTOOL_LINK_MODE_MASK_NBITS - MLX5E_MIN_PTYS_EXT_LINK_MODE_BIT;
-	__ETHTOOL_DECLARE_LINK_MODE_MASK(modes);
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(modes) = {0,};
 
 	bitmap_set(modes, MLX5E_MIN_PTYS_EXT_LINK_MODE_BIT, size);
 	return bitmap_intersects(modes, adver, __ETHTOOL_LINK_MODE_MASK_NBITS);