fpga: region: fix kernel-doc

fpga: region: fix kernel-doc

- Fix the following warnings issued by the kernel-doc script:

drivers/fpga/fpga-region.c:46: warning: No description found for return value of 'fpga_region_get'
drivers/fpga/fpga-region.c:97: warning: No description found for return value of 'fpga_region_program_fpga'
drivers/fpga/fpga-region.c:295: warning: No description found for return value of 'fpga_region_init'

- Remove the "and registers a reconfig notifier" part from the description
  of fpga_region_init() since it does not register an of_overlay notifier
  anymore.

- Remove the outdated "if @np is not an FPGA Region" case from the return
  description of fpga_region_get() and replace it with the case when
  try_module_get() fails.

Signed-off-by: Marco Pagani <marpagan@redhat.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20230706142755.124879-2-marpagan@redhat.com
Signed-off-by: Xu Yilun <yilun.xu@intel.com>