drm/vmwgfx: Remove set but not used variable 'fb_offset, fb_depth'
Fixes gcc '-Wunused-but-set-variable' warning:
drivers/gpu/drm/vmwgfx/vmwgfx_fb.c: In function 'vmw_fb_init':
drivers/gpu/drm/vmwgfx/vmwgfx_fb.c:645:29: warning:
variable 'fb_offset' set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/vmwgfx/vmwgfx_fb.c:645:19: warning:
variable 'fb_depth' set but not used [-Wunused-but-set-variable]