drm/i915: fix regression with uncore refactoring.

This was causing infinite recursion on snb/ivb.

Fixes: 5716c8c6

 ("drm/i915/uncore: split the fw get function into separate vfunc")
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211004003133.2279446-1-airlied@gmail.com