nvfx: dont swizzle stuff into GART

nvfx: dont swizzle stuff into GART

swzsurf doesn't support GART

Thanks to Marcin Kościelnicki <koriakin@0x04.net> for spotting that !

This fixes corruption in etracer and the following related errors :
[14381.551927] [drm] nouveau 0000:01:00.0: PGRAPH_ERROR - nSource:
PROTECTION_ERROR, nStatus: INVALID_STATE
[14381.551945] [drm] nouveau 0000:01:00.0: PGRAPH_ERROR - Ch 2/2 Class
0x039e Mthd 0x0184 Data 0x00001cd9:0x00001cd9

Signed-off-by: Xavier Chantry <chantry.xavier@gmail.com>
Adapted by Luca Barbieri for mesa master.