script, perf: look for sideband files in current directory when computing opts
script, perf: look for sideband files in current directory when computing opts

In script/perf-get-opts.bash, we look for sideband files in the directory of the
perf.data file.  Look instead in the current working directory.

Change-Id: I27c7fb2a014c9ef7e37f22d11bab8b1952324ef4
Signed-off-by: Markus Metzger <5f675b2b36595f90898e014b548ff7d9bbff2ab7@intel.com>

01org/processor-trace,01org/processor-trace,01org/processor-trace