[llvm-objdump] Prevent variable locations to overlap short comments

For now, the source variable locations are printed at about the same
space as the comments for disassembled code, which can make some ranges
for variables disappear if a line contains comments, for example:

                                        ┠─ bar = W1
0:  add x0, x2, #2, lsl #12     // =8192┃
4:  add z31.d, z31.d, #65280    // =0xff00
8:  nop                                 ┻

The patch shifts the report a bit to allow printing comments up to
approximately 16 characters without interferences.

Differential Revision: https://reviews.llvm.org/D104700