mips[el]: fix cast from pointer to integer of different size
mips[el]: fix cast from pointer to integer of different size

This fixes GCC 4.9.3 warnings (Linux/mipsel):

In file included from dwarf/Lfind_unwind_table.c:4:0:
dwarf/Gfind_unwind_table.c: In function '_ULmips_dwarf_find_unwind_table':
dwarf/Gfind_unwind_table.c:140:14: warning: cast from pointer to integer of
different size [-Wpointer-to-int-cast]
       addr = (unw_word_t) (hdr + 1);
              ^
dwarf/Gfind_unwind_table.c:196:50: warning: cast from pointer to integer of
different size [-Wpointer-to-int-cast]
                                        + (addr - (unw_word_t) edi->ei.image
                                                  ^
dwarf/Gfind_unwind_table.c:202:40: warning: cast from pointer to integer of
different size [-Wpointer-to-int-cast]
                                     + ((unw_word_t) hdr - (unw_word_t)
edi->ei.image
                                        ^
dwarf/Gfind_unwind_table.c:202:59: warning: cast from pointer to integer of
different size [-Wpointer-to-int-cast]
                                     + ((unw_word_t) hdr - (unw_word_t)
edi->ei.image
                                                           ^

unkadoug/libunwind,yuyichao/libunwind,rantala/libunwind,djwatson/libunwind,unkadoug/libunwind,vtjnash/libunwind,djwatson/libunwind,unkadoug/libunwind,frida/libunwind,vtjnash/libunwind,yuyichao/libunwind,rantala/libunwind,djwatson/libunwind,rantala/libunwind,frida/libunwind,libunwind/libunwind,vtjnash/libunwind,yuyichao/libunwind,frida/libunwind,libunwind/libunwind,libunwind/libunwind