fpga: dfl: remove unused function is_dfl_feature_present()

The function is_dfl_feature_present() was added but never used.

Fixes: 5b57d02a ("fpga: dfl: add feature device infrastructure")
Signed-off-by: Peter Colberg <peter.colberg@intel.com>
Reviewed-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20240415235743.3045-1-peter.colberg@intel.com


Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>