scripts: Specify the stats to take into account

scripts: Specify the stats to take into account

There are many more stats on buildstats that 'Elapsed time', so make the script
more flexible to support all stats. Some cmd line examples:

$ buildstats.sh -s 'utime'

Buildstats' data covers proc's stats in different areas, including CPU times,
IO, program system resources and child program system resources. In order
to print values on each of these sets from command line, one can use the
following:

$ buildstats.sh -H -s 'TIME' | less

$ buildstats.sh -H -s 'IO' | less

and 'RUSAGE' and 'CHILD_RUSAGE' for program and program's child system
resources.

(From OE-Core rev: 81479b191287ccbf4cf94fa2d0ad46813091bca1)

Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>