ldso/mips: Clean up warnings

ldso/mips: Clean up warnings

Trivial fixes for these warnings:

  CC ldso/libdl/libdl.oS
In file included from ldso/ldso/ldso.c:46:0:
ldso/ldso/mips/elfinterp.c:88:1: warning: no previous prototype for '__dl_runtime_pltresolve'
ldso/ldso/ldso.c: In function '_dl_get_ready_to_run':
ldso/ldso/ldso.c:475:5: warning: assignment makes pointer from integer without a cast
In file included from ldso/ldso/ldso.c:1097:0:
ldso/ldso/dl-elf.c: In function '_dl_load_elf_shared_library':
ldso/ldso/dl-elf.c:811:3: warning: assignment makes pointer from integer without a cast

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>