util/cb2replay.sh: Prune superfluous coreboot output

With certain Kconfig options, coreboot may prepend a monotonic
timestamp to the VGA trace output. A line of output looks like:

 [00083f44]c000:3b69 inb(0x03c3) = 0x20

If we don't remove this monotonic timestamp, it will survive in the
C code. Get rid of it.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
util/cb2replay.sh: Separate interrupt handlers from main init

coreboot can be instructed to output information pertaining to
realmode interrupt handlers installed by the VGA BIOS< and will also
output traces of interrupt execution. It is useful to trace where an
interrupt begins, and where it ends. Adjust the script to separate
interrupt traces from the main initialization trace.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>