fpga: region: Add fpga-region property 'encrypted-fpga-config'

Add fpga-region property to allow passing the fact that the bitstream is
encrypted to the fpga-region and ultimately to the low-level driver.
Signed-off-by: Moritz Fischer <mdf@kernel.org>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/fpga/fpga-region.txt

@@ -186,6 +186,7 @@ Optional properties:
 	otherwise full reconfiguration is done.
 - external-fpga-config : boolean, set if the FPGA has already been configured
 	prior to OS boot up.
+- encrypted-fpga-config : boolean, set if the bitstream is encrypted
 - region-unfreeze-timeout-us : The maximum time in microseconds to wait for
 	bridges to successfully become enabled after the region has been
 	programmed.

drivers/fpga/fpga-region.c

@@ -339,6 +339,7 @@ static int child_regions_with_firmware(struct device_node *overlay)
  *
  *   firmware-name         : program the FPGA
  *   external-fpga-config  : FPGA is already programmed
+ *   encrypted-fpga-config : FPGA bitstream is encrypted
  *
  * The overlay can add other FPGA regions, but child FPGA regions cannot have a
  * firmware-name property since those regions don't exist yet.
@@ -373,6 +374,9 @@ static int fpga_region_notify_pre_apply(struct fpga_region *region,
 	if (of_property_read_bool(nd->overlay, "external-fpga-config"))
 		info->flags |= FPGA_MGR_EXTERNAL_CONFIG;
 
+	if (of_property_read_bool(nd->overlay, "encrypted-fpga-config"))
+		info->flags |= FPGA_MGR_ENCRYPTED_BITSTREAM;
+
 	of_property_read_string(nd->overlay, "firmware-name", &firmware_name);
 
 	of_property_read_u32(nd->overlay, "region-unfreeze-timeout-us",