fpga: dfl: convert features from flexible array member to separate array

fpga: dfl: convert features from flexible array member to separate array

Use a separate array allocation for features and substitute a pointer
for the flexible array member in the feature device data. A subsequent
commit will add another array for resources. The current commit converts
the flexible array member to a separate allocation for consistency.

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/20241120011035.230574-12-peter.colberg@intel.com
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>