net/mlx5e: xsk: Flush RQ on XSK activation to save memory

The regular RQ remains open after opening an XSK socket, in order to
guarantee that closing the XSK socket never fails due to an error when
reopening the regular RQ.

To save memory, the regular RQ can be deactivated and flushed, releasing
all pages, when an XSK socket is open.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>