net/mlx5: Move device memory management to mlx5_core

Move the device memory allocation and deallocation commands
SW ICM memory to mlx5_core to expose this API for all
mlx5_core users.

This comes as preparation for supporting SW steering in kernel
where it will be required to allocate and register device
memory for direct rule insertion.

In addition, an API to register this device memory for future
remote access operations is introduced using the create_mkey
commands.

Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>