run: exit __parse_trace_file() early if there's nothing to parse
run: exit __parse_trace_file() early if there's nothing to parse

Now that we go through two files (the normal trace and the raw trace),
we can waste a bit of time trying to parse the raw trace when none of
our traces ask for it (the default case).  Exit early if we don't have
anything to parse.

Change-Id: Ib3f15cea6d263f24a4a7cc9652ad5e75ac7ad9aa
Signed-off-by: Javi Merino <cc0c468e3dcd5ee425259d298d905a60f8330bcf@arm.com>

ARM-software/trappy,bjackman/trappy,ARM-software/trappy,derkling/trappy,bjackman/trappy,JaviMerino/trappy,joelagnel/trappy,sinkap/trappy,ARM-software/trappy,derkling/trappy,derkling/trappy,joelagnel/trappy,bjackman/trappy,JaviMerino/trappy,bjackman/trappy,joelagnel/trappy,sinkap/trappy,ARM-software/trappy,JaviMerino/trappy,sinkap/trappy,sinkap/trappy,joelagnel/trappy