[PATCH] win32u: Use null driver to handle virtual display devices.

[Jacek Caban]

All drivers support UpdateDisplayDevices now, so we can avoid a server 
call by being explicit in the null driver.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=52180
Signed-off-by: Jacek Caban <jacek(a)codeweavers.com>
---
  dlls/win32u/driver.c    |  1 +
  dlls/win32u/sysparams.c | 48 ++++++++++++-----------------------------
  2 files changed, 15 insertions(+), 34 deletions(-)