LU-56 ptlrpc: clean up ptlrpc svc initializing APIs

LU-56 ptlrpc: clean up ptlrpc svc initializing APIs

Both ptlrpc_init_svc and ptlrpc_init_svc_conf have long parameter list
and difficult for user, also, it doesn't make too much sense to keep
both of them. This patch will merge them to a new one
ptlrpc_register_service, and improve the structured parameter
ptlrpc_service_conf and make it more clear for user.
This is the first patch for ptlrpc service SMP improvements, more
patches depending on this will come soon.

Signed-off-by: Liang Zhen <liang@whamcloud.com>
Change-Id: I7b2932d4235fb418bee8e9d65f8b3e4f62d2849e
Reviewed-on: http://review.whamcloud.com/2878
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: wangdi <di.wang@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>