drm/i915/uc: Trivial s/dev_priv/i915 in intel_uc.c

Some functions already use i915 name instead of dev_priv.
Let's rename this param in all remaining functions, except
those that still use legacy macros.

v2: don't forget about function descriptions (Sagar)
v3: rebased
v4: rebased
v5: rebased, pulled out from the series

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180525121858.53928-1-michal.wajdeczko@intel.com