BugLink: http://bugs.launchpad.net/bugs/1540390

Add i915_bpo_* functions for use with the ubuntu/i915 driver.

i915_gpu_turbo_disable => i915_bpo_gpu_turbo_disable
i915_gpu_busy => i915_bpo_gpu_busy
i915_gpu_lower => i915_bpo_gpu_lower
i915_gpu_raise => i915_bpo_gpu_raise
i915_read_mch_val => i915_bpo_read_mch_val
Signed-off-by: Timo Aaltonen <timo.aaltonen@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>