drm/i915/uc: replace uc init/fini misc

The "misc" terminology doesn't clearly explain what we intend to cover
in this phase. The only thing we used ot do in there apart from FW fetch
was initializing the log workqueue, with the latter being required only in
the very rare case where we enable the log relay. As we no longer create
our own workqueue, piggybacking on the system_highpri_wq instead, we can
rename the function to clarify that they only fetch/release the blobs.

v2: only create log wq when needed (Michal), reword commit msg
accordingly
v3: after rebase the wq is gone, reword commit msg accordingly

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190713100016.8026-2-chris@chris-wilson.co.uk
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>