net/mlx5: Query device memory capabilities

This patch adds querying of device memory capabilities by the mlx5_core
driver during initialization.

Device memory capabilities is a new capability type and structure
which contains the necessary data that is needed for future device
memory allocation.

The presence of this new capabilities struct is indicated in the
general capabilities struct which is queried first by the driver.
If the presence bit is set, the driver will also query the new
capabilities struct and save it in the device context.

Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>