fpga: dfl: return platform data from dfl_fpga_inode_to_feature_dev_data()

fpga: dfl: return platform data from dfl_fpga_inode_to_feature_dev_data()

Refactor dfl_fpga_inode_to_feature_dev() to directly return the feature
device platform data instead of the platform device, and retrieve the
device from the data. The null pointer checks are not needed since the
platform device is guaranteed to have associated feature device data.

This patch is part of a refactoring of the internal DFL APIs to move
the feature device data into a new struct dfl_feature_dev_data which
lifetime is independent of the corresponding platform device.

Signed-off-by: Peter Colberg <peter.colberg@intel.com>
Reviewed-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Reviewed-by: Basheer Ahmed Muddebihal <basheer.ahmed.muddebihal@linux.intel.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20241120011035.230574-3-peter.colberg@intel.com
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>