net/mlx5e: Change VF representors' RQ type

The representors' RQ size was not large enough for them to achieve
high enough performance, and therefore needed to be enlarged, while
suffering a minimum hit to its memory usage. To achieve this the
representors RQ size was increased, and its type was changed to be a
striding RQ if it is supported.

Towards that goal the following changes were made:

* Extracted the sequence for setting the standard netdev's RQ parmas
  into a function

* Replaced the sequence for setting the representor's RQ params with
  the standard sequence

The impact of this change can be seen in the following measurements
taken on a setup of a VM over a VF, connected to OVS via the VF
representor, to an external host:

Before current change:
                     TCP Throughput [Gb/s]
VM to external host         ~  7.2

With the current change (measured with a striding RQ):
                     TCP Throughput [Gb/s]
VM to external host         ~ 23.5

Each representor now consumes 2 [MB] of memory for its packet
buffers.

Signed-off-by: Gavi Teitz <gavi@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>