tools/power turbostat: add [-d MSR#][-D MSR#] options to print counter deltas

 # turbostat -d 0x34
is useful for printing the number of SMI's within an interval
on Nehalem and newer processors.

where
 # turbostat -m 0x34
will simply print out the total SMI count since reset.

Suggested-by: Andi Kleen
Signed-off-by: Len Brown <len.brown@intel.com>