fpga: allow programming fpga from FIT image for all FPGA drivers

This drops the limit that fpga is only loaded from FIT images for Xilinx.
This is done by moving the 'partial' check from 'common/image.c' to
'drivers/fpga/xilinx.c' (the only driver supporting partial images yet)
and supplies a weak default implementation in 'drivers/fpga/fpga.c'.

Signed-off-by: Simon Goldschmidt <sgoldschmidt@de.pepperl-fuchs.com>
Tested-by: Michal Simek <michal.simek@xilinx.com> (On zcu102)
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

drivers/fpga/fpga.c

@@ -170,6 +170,15 @@ int fpga_add(fpga_type devtype, void *desc)
 	return devnum;
 }
 
+/*
+ * Return 1 if the fpga data is partial.
+ * This is only required for fpga drivers that support bitstream_type.
+ */
+int __weak fpga_is_partial_data(int devnum, size_t img_len)
+{
+	return 0;
+}
+
 /*
  * Convert bitstream data and load into the fpga
  */