drm/i915/guc: Avoid reclaim locks during reset

During reset, we must be very selective in which locks we take as most
are tainted by being held across a wait or reclaim (kmalloc) which
implicitly waits. Inside the guc reset path, we reset the ADS to sane
defaults, but must keep it pinned from initialisation to avoid having to
pin it during reset.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190701100502.15639-1-chris@chris-wilson.co.uk