uio: dfl: add vendor-specific feature id

Add a Device Feature List (DFL) feature id as a generic mechanism
to expose a vendor-specific FPGA IP to user space. The feature id
is intended for use with IPs that do not need any kernel services
beyond exposure to user space through the UIO DFL driver.

The feature id is used in, e.g., Intel Oak Springs Canyon IPUs
to expose various IPs to user space, e.g., Network Controller
Sideband Interface (NC-SI), BaseNIC, and VirtIO management.

Link: https://github.com/OPAE/dfl-feature-idSigned-off-by: Peter Colberg <peter.colberg@intel.com>
Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Reviewed-by: Russ Weight <russell.h.weight@intel.com>
Link: https://lore.kernel.org/r/20230531030737.12989-1-peter.colberg@intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uio/uio_dfl.c

@@ -46,11 +46,13 @@ static int uio_dfl_probe(struct dfl_device *ddev)
 
 #define FME_FEATURE_ID_ETH_GROUP	0x10
 #define FME_FEATURE_ID_HSSI_SUBSYS	0x15
+#define FME_FEATURE_ID_VENDOR_SPECIFIC	0x23
 #define PORT_FEATURE_ID_IOPLL_USRCLK	0x14
 
 static const struct dfl_device_id uio_dfl_ids[] = {
 	{ FME_ID, FME_FEATURE_ID_ETH_GROUP },
 	{ FME_ID, FME_FEATURE_ID_HSSI_SUBSYS },
+	{ FME_ID, FME_FEATURE_ID_VENDOR_SPECIFIC },
 	{ PORT_ID, PORT_FEATURE_ID_IOPLL_USRCLK },
 	{ }
 };