devlink: convert flash_update to use params structure

The devlink core recently gained support for checking whether the driver
supports a flash_update parameter, via `supported_flash_update_params`.
However, parameters are specified as function arguments. Adding a new
parameter still requires modifying the signature of the .flash_update
callback in all drivers.

Convert the .flash_update function to take a new `struct
devlink_flash_update_params` instead. By using this structure, and the
`supported_flash_update_params` bit field, a new parameter to
flash_update can be added without requiring modification to existing
drivers.

As before, all parameters except file_name will require driver opt-in.
Because file_name is a necessary field to for the flash_update to make
sense, no "SUPPORTED" bitflag is provided and it is always considered
valid. All future additional parameters will require a new bit in the
supported_flash_update_params bitfield.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Cc: Jiri Pirko <jiri@mellanox.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michael Chan <michael.chan@broadcom.com>
Cc: Bin Luo <luobin9@huawei.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Ido Schimmel <idosch@mellanox.com>
Cc: Danielle Ratson <danieller@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>