gallium: introduce get_device_vendor() entrypoint for pipes

This will be needed by Clover to return the correct information
to CL_DEVICE_VENDOR info queries.

Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

src/gallium/docs/source/screen.rst

@@ -462,6 +462,12 @@ get_vendor
 
 Returns the screen vendor.
 
+get_device_vendor
+^^^^^^^^^^^^^^^^^
+
+Returns the actual vendor of the device driving the screen
+(as opposed to the driver vendor).
+
 .. _get_param:
 
 get_param

src/gallium/include/pipe/p_screen.h

@@ -71,6 +71,14 @@ struct pipe_screen {
 
    const char *(*get_vendor)( struct pipe_screen * );
 
+   /**
+    * Returns the device vendor.
+    *
+    * The returned value should return the actual device vendor/manufacturer,
+    * rather than a potentially generic driver string.
+    */
+   const char *(*get_device_vendor)( struct pipe_screen * );
+
    /**
     * Query an integer-valued capability/parameter/limit
     * \param param  one of PIPE_CAP_x