turbostat: Factor out common function to open file and exit on failure

Several different functions in turbostat contain the same pattern of
opening a file and exiting on failure.  Factor out a common fopen_or_die
function for that.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --cc tools/power/x86/turbostat/turbostat.c
Simple merge