x86: msr-index.h: Correct SNB_C1/C3_AUTO_UNDEMOTE defines

According to the Intel Software Developers' Manual, Vol. 4, Order No.
335592, these macros have been reversed since they were added in the
initial turbostat commit. The reversed definitions were presumably
copied from turbostat.c to this file.

Fixes: 9c63a650 ("tools/power/x86/turbostat: share kernel MSR #defines")
Signed-off-by: Matt Turner <mattst88@gmail.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Len Brown <len.brown@intel.com>