ShellPkg: Update ping command options to sync with Spec

ShellPkg: Update ping command options to sync with Spec

This patch is used to update ping command options to sync
with shell2.2 Spec.
Considering the backward compatible issue, the patch keeps
‘-_s’ command option unchanged, only add the new option '-s'
and make the old option '-_s' function same as new one.

Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>