perf tools powerpc: Add support for generating bpf prologue

Generalize existing macros to serve the purpose.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Ian Munsie <imunsie@au1.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1462461799-17518-1-git-send-email-naveen.n.rao@linux.vnet.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>