mlxsw: pci: Add support for new reset flow

The driver resets the device during probe and during a devlink reload.
The current reset method reloads the current firmware version or a
pending one, if one was previously flashed using devlink. However, the
current reset method does not result in a PCI hot reset, preventing the
PCI firmware from being upgraded, unless the system is rebooted.

To solve this problem, a new reset command (6) was implemented in the
firmware. Unlike the current command (1), after issuing the new command
the device will not start the reset immediately, but only after a PCI
hot reset.

Implement the new reset method by first verifying that it is supported
by the current firmware version by querying the Management Capabilities
Mask (MCAM) register. If supported, issue the new reset command (6) via
MRSR register followed by a PCI reset by calling
__pci_reset_function_locked().

Once the PCI firmware is operational, go back to the regular reset flow
and wait for the entire device to become ready. That is, repeatedly read
the "system_status" register from the BAR until a value of "FW_READY"
(0x5E) appears.

Tested:

 # for i in $(seq 1 10); do devlink dev reload pci/0000:01:00.0; done

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>