drm: drop select of SLOW_WORK

slow-work got killed in commit 181a51f6. This means that since v2.6.36
there is no Kconfig symbol SLOW_WORK. Apparently selecting that symbol
is a nop. Drop that select.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/Kconfig

@@ -9,7 +9,6 @@ menuconfig DRM
 	depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && MMU
 	select I2C
 	select I2C_ALGOBIT
-	select SLOW_WORK
 	help
 	  Kernel-level support for the Direct Rendering Infrastructure (DRI)
 	  introduced in XFree86 4.0. If you say Y here, you need to select