xsk: Remove unused xsk_buff_discard

The previous commit removed the last usage of xsk_buff_discard in mlx5e,
so the function that is no longer used can be removed.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
CC: "Björn Töpel" <bjorn@kernel.org>
CC: Magnus Karlsson <magnus.karlsson@intel.com>
CC: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/xdp_sock_drv.h

@@ -107,13 +107,6 @@ static inline void xsk_buff_free(struct xdp_buff *xdp)
 	xp_free(xskb);
 }
 
-static inline void xsk_buff_discard(struct xdp_buff *xdp)
-{
-	struct xdp_buff_xsk *xskb = container_of(xdp, struct xdp_buff_xsk, xdp);
-
-	xp_release(xskb);
-}
-
 static inline void xsk_buff_set_size(struct xdp_buff *xdp, u32 size)
 {
 	xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;