net/mlx5: Refactor FTE and FG creation code

Split the creation code to two parts:
1) Object allocation - allocate the steering node and initialize
its resources.

2) The firmware command execution.

Adding active flag to each node - this flag indicates if the
object exists in the hardware or not, if not we don't free
the hardware resource in error flow.

This change will give us the ability to take write lock on the
parent node (e.g. FG for FTE creationg) only on the first part.

Signed-off-by: Maor Gottlieb <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>

Author: Maor Gottlieb