cs-etm: associating output packet with CPU they executed on

This patch adds the required mechanic to quickly lookup the CPU number
associated with a traceID.  That way the CPU that executed the code
conveyed by a decoded packet can be identified, without having to
do unecessary translations.

Using this new functionality the "cs-trace-disasm.py" script is
enhanced to output the file and CPU number the code has been
executed on:

FILE: /lib/aarch64-linux-gnu/ld-2.21.so CPU: 3
          7fab57fd80:   910003e0        mov     x0, sp
          7fab57fd84:   94000d53        bl      7fab5832d0 <free@plt+0x3790>
FILE: /lib/aarch64-linux-gnu/ld-2.21.so CPU: 3
          7fab5832d0:   d11203ff        sub     sp, sp, #0x480
FILE: /lib/aarch64-linux-gnu/ld-2.21.so CPU: 3
          7fab5832d4:   a9ba7bfd        stp     x29, x30, [sp,#-96]!
          7fab5832d8:   910003fd        mov     x29, sp
          7fab5832dc:   a90363f7        stp     x23, x24, [sp,#48]
          7fab5832e0:   9101e3b7        add     x23, x29, #0x78
          7fab5832e4:   a90573fb        stp     x27, x28, [sp,#80]
          7fab5832e8:   a90153f3        stp     x19, x20, [sp,#16]
          7fab5832ec:   aa0003fb        mov     x27, x0
          7fab5832f0:   910a82e1        add     x1, x23, #0x2a0
          7fab5832f4:   a9025bf5        stp     x21, x22, [sp,#32]
          7fab5832f8:   a9046bf9        stp     x25, x26, [sp,#64]
          7fab5832fc:   910102e0        add     x0, x23, #0x40
          7fab583300:   f800841f        str     xzr, [x0],#8
          7fab583304:   eb01001f        cmp     x0, x1
          7fab583308:   54ffffc1        b.ne    7fab583300 <free@plt+0x37c0>

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>