net/mlx5e: Turn XSK ICOSQ into a general asynchronous one

There is an upcoming demand (in downstream patches) for
an ICOSQ to be populated out of the NAPI context, asynchronously.

There is already an existing one serving XSK-related use case.
In this patch, promote this ICOSQ to serve as general async ICOSQ,
to be used for XSK and non-XSK flows.

As part of this, the reg_umr bit of the SQ context is now set
(if capable), as the general async ICOSQ should support possible
posts of UMR WQEs.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>