fpga: fpga-mgr: Add devm_fpga_mgr_register() API

fpga: fpga-mgr: Add devm_fpga_mgr_register() API

Add a devm_fpga_mgr_register() API that can be used to register a FPGA
Manager that was created using devm_fpga_mgr_create().

Introduce a struct fpga_mgr_devres that makes the devres
allocation a little bit more readable and gets reused for
devm_fpga_mgr_create() devm_fpga_mgr_register().

Reviewed-by: Tom Rix <trix@redhat.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
Link: https://lore.kernel.org/r/20201115195127.284487-2-mdf@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>