Function i915_gem_batch_pool_init() failed to follow obj-verb
naming schema. Fix that by swapping function parameters.
While here, change license text to SPDX format.

v2: use intel_engine_init_batch_pool (Chris) as proxy (Michal)
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180308095037.18264-3-michal.wajdeczko@intel.com