[MIPS] __dso_handle.S and __dso_handle_so.S not needed.

Global hidden variable __dso_handle is now declared in:
       bionic/libc/private/__dso_handle.h

Change-Id: I8e951a8d7c65877bafc1be23a7fff6d44d3a2846
Signed-off-by: Pete Delaney <piet.delaney@imgtec.com>
Signed-off-by: Chao-Ying Fu <chao-ying.fu@imgtec.com>