bpf: Undo incorrect __reg_bound_offset32 handling

      Anatoly has been fuzzing with kBdysch harness and reported a hang in
one of the outcomes:

  0: (b7) r0 = 808464432
  1: (7f) r0 >>= r0
  2: (14) w0 -= 808464432
  3: (07) r0 += 808464432
  4: (b7) r1 = 808464432
  5: (de) if w1 s<= w0 goto pc+0
   R0_w=invP(id=0,umin_value=808464432,umax_value=5103431727,var_off=(0x30303020;0x10000001f)) R1_w=invP808464432 R10=fp0
  6: (07) r0 += -2144337872
  7: (14) w0 -= -1607454672
  8: (25) if r0 > 0x30303030 goto pc+0
   R0_w=invP(id=0,umin_value=271581184,umax_value=271581311,var_off=(0x10300000;0x7f)) R1_w=invP808464432 R10=fp0
  9: (76) if w0 s>= 0x303030 goto pc+2
  12: (95) exit

  from 8 to 9: safe

  from 5 to 6: R0_w=invP(id=0,umin_value=808464432,umax_value=5103431727,var_off=(0x30303020;0x10000001f)) R1_w=invP808464432 R10=fp0
  6: (07) r0 += -2144337872
  7: (14) w0 -= -1607454672
  8: (25) if r0 > 0x30303030 goto pc+0
   R0_w=invP(id=0,umin_value=271581184,umax_value=271581311,var_off