drm/i915/uc: Make intel_uc_prepare_fw() static

drm/i915/uc: Make intel_uc_prepare_fw() static

There is no need to expose this function as it is called from
one function only. Also move it up to avoid forward declaration.

v2: drop intel_ prefix (Oscar) and rename to fetch_uc_fw (Michal)

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170327094510.167400-1-michal.wajdeczko@intel.com
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>