Encoding: Dynamically select one mechanism to construct encoding command buffer for...

Encoding: Dynamically select one mechanism to construct encoding command buffer for each frame on Haswell and Gen7/Gen6

v2:remove the warning when compiling

v1: combine the Haswell and Gen7/6 patch together

Currently it uses the fixed policy to construct encoding command buffer.
(Use CPU or GPU). And it is statically compiled.
But sometimes it needs to choose the different mechanism on the fly instead
of statically compiled mode.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: pjl <cecilia.peng@intel.com>
Signed-off-by: Pengfei Qu <Pengfei.Qu@intel.com>
(cherry picked from commit 89463c30a9ce2740603f36f1000da54b8b5c731b)