xsk: Remove unused inline function xsk_buff_discard()

commit f2f167583601 ("xsk: Remove unused xsk_buff_discard")
left behind this, remove it.

Signed-off-by: YueHaibing <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Acked-by: Maciej Fijalkowski <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

include/net/xdp_sock_drv.h

···
 {
 }
 
-static inline void xsk_buff_discard(struct xdp_buff *xdp)
-{
-}
-
 static inline void xsk_buff_set_size(struct xdp_buff *xdp, u32 size)
 {
 }