drm/i915: use intel_uncore in fw get/put internal paths

Get/put functions used outside of uncore.c are updated in the next
patch for a nicer split.

v2: use dev_priv where we still have it (Paulo)

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190319183543.13679-3-daniele.ceraolospurio@intel.com