MGS-4376 [#imx-1238] fix low performance with CMA allocator

MGS-4376 [#imx-1238] fix low performance with CMA allocator

there are lots of PFNs busy message when run GPU tests:
 [  622.370671] alloc_contig_range: [4ea70, 4ea7c) PFNs busy
 [  626.518072] alloc_contig_range: [4ea90, 4ea9c) PFNs busy

this problem is related with CMA migration for fragments,

move CMA allocator after GFP to avoid memory migration,
also fix CMA preempt for contiguous memory request.

can improve CTS and gpubench benchmarks on M850D.

Signed-off-by: Xianzhong <xianzhong.li@nxp.com>
(cherry picked from commit ad77ed61b72c8362b04361acd2deb685fee15436)