devlink: Add support for devlink resource abstraction

devlink: Add support for devlink resource abstraction

Add support for devlink resource abstraction. The resources are
represented by a tree based structure and are identified by a name and
a size. Some resources can present their real time occupancy.

First the resources exposed by the driver can be observed, for example:

$devlink resource show pci/0000:03:00.0
pci/0000:03:00.0:
  name kvd size 245760 unit entry
    resources:
      name linear size 98304 occ 0 unit entry size_min 0 size_max 147456 size_gran 128
      name hash_double size 60416 unit entry size_min 32768 size_max 180224 size_gran 128
      name hash_single size 87040 unit entry size_min 65536 size_max 212992 size_gran 128

Some resource's size can be changed. Examples:

$devlink resource set pci/0000:03:00.0 path /kvd/hash_single size 73088
$devlink resource set pci/0000:03:00.0 path /kvd/hash_double size 74368

The changes do not apply immediately, this can be validate by the 'size_new'
attribute, which represents the pending changed size. For example

$devlink resource show pci/0000:03:00.0
pci/0000:03:00.0:
  name kvd size 245760 unit entry size_valid false
  resources:
    name linear size 98304 size_new 147456 occ 0 unit entry size_min 0 size_max 147456 size_gran 128
    name hash_double size 60416 unit entry size_min 32768 size_max 180224 size_gran 128
    name hash_single size 87040 unit entry size_min 65536 size_max 212992 size_gran 128

In case of a pending change the nested resources present an indication
for a valid configuration of its children (sum of its children sizes
doesn't exceed the parent's size).

In order for the changes to take place hot reload is needed. The hot
reload through devlink will be introduced in the following patch.

Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>