xdp: unpin xdp umem pages in error path

[ Upstream commit fb89c394 ]

Fix mem leak caused by missed unpin routine for umem pages.

Fixes: 8aef7340

 ("xsk: introduce xdp_umem_page")
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>