Fix GPREL16 references emitted by PS2 GCC

[1superchip]

PS2 GCC emits R_MIPS_GPREL16 relocations for data that can be referenced by gp. The compiler emits an addend to all instructions that have the R_MIPS_GPREL16 relocation. Replacing the relocation of .sbss+0x4000-addend to the symbol that it points to would improve the diff for PS2 GCC objects.

objdump output of the object:

00000008 <CBuffGetStr__Fi>:
   8:   04800005        bltz    a0,20 <CBuffGetStr__Fi+0x18>
   c:   00000000        nop
  10:   8f82c000        lw      v0,-16384(gp)
                        10: R_MIPS_GPREL16      .sbss+0x4000
  14:   0082102a        slt     v0,a0,v0
  18:   54400003        bnezl   v0,28 <CBuffGetStr__Fi+0x20>
  1c:   8f82c004        lw      v0,-16380(gp)
                        1c: R_MIPS_GPREL16      .sbss+0x4000
  20:   03e00008        jr      ra
  24:   0000102d        move    v0,zero
  28:   8f83c00c        lw      v1,-16372(gp)
                        28: R_MIPS_GPREL16      .sbss+0x4000
  2c:   00441018        mult    v0,v0,a0
  30:   03e00008        jr      ra
  34:   00621021        addu    v0,v1,v0

Relocations in the object:

RELOCATION RECORDS FOR [.text]:
OFFSET   TYPE              VALUE
00000010 R_MIPS_GPREL16    .sbss+0x00004000
0000001c R_MIPS_GPREL16    .sbss+0x00004000
00000028 R_MIPS_GPREL16    .sbss+0x00004000

Relevant symbols in the object:

00000000 l       .sbss  00000000 CBuffNum
00000004 l       .sbss  00000000 CBuffMaxLen
0000000c l       .sbss  00000000 CBuffStr
00000008 l       .sbss  00000000 CBuffMaxNum