va/win32: Change default driver name to full path

As in Win LoadLibrary (aliased to dlopen) supports the file string
to have multiple semantics. I left only the vaon12_drv_video filename,
which will first still try to open .\vaon12_drv_video.dll and then
attempt again using the default Windows library search order.

For example, from the LoadLibrary documentation:

- If no file name extension is specified in the lpFileName parameter,
  the default library extension .dll is appended.

- When no path is specified, the function searches for loaded modules
  whose base name matches the base name of the module to be loaded.
  If the name matches, the load succeeds. Otherwise, the function searches
  for the file. The first directory searched is the directory containing
  the image file used to create the calling process...

Signed-off-by: Sil Vilerino <sivileri@microsoft.com>

Author: sivileri

va/win32/va_win32.c

@@ -35,7 +35,7 @@
  * which will be selected when provided with an adapter LUID which
  * does not have a registered VA driver
 */
-const char VAAPI_DEFAULT_DRIVER_NAME[] = "vaon12";
+const char VAAPI_DEFAULT_DRIVER_NAME[] = "vaon12_drv_video";
 
 typedef struct _VADisplayContextWin32 {
     LUID adapter_luid;