drm/i915/guc: GuC suspend path cleanup

Adding a call to intel_uc_suspend in i915_gem_suspend, which
is a common point for the suspend/resume and hibernate paths.
This fixes an unbalanced call that causes issues with the CTB
register/deregister.

v2: Making the call unconditional (Daniele)
	Moving the call to after the GEM_BUG_ON (Chris)

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190321203804.6845-1-sujaritha.sundaresan@intel.com