HSW: Use the drm flag I915_EXEC_ENABLE_SLM to set L3 control config.

HSW: Use the drm flag I915_EXEC_ENABLE_SLM to set L3 control config.

Because LRI commands will be converted to NOOP, add the I915_EXEC_ENABLE_SLM
flag to the drm kernal driver, to enable SLM in the L3. Set the flag when
application use slm. Still keep the L3 config in the batch buffer for fulsim.
Also create and use the openCL own context when exec, to avoid affect the other context.

Signed-off-by: Yang Rong <rong.r.yang@intel.com>
Reviewed-by: Junyan He <junyan.he@inbox.com>