eal: split CPU flags operations to architecture specific

This patch splits CPU flags related operations from DPDK and push them
to architecture specific arch directories, so that other processor
architecture can implement its own CPU flag functions to support DPDK.

Signed-off-by: Chao Zhu <bjzhuc@cn.ibm.com>
Signed-off-by: David Marchand <david.marchand@6wind.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>