x86: Change warning message in TSC calibration.

When calibration against PIT fails, the warning that we print is misleading.
In a virtualized environment the VM may get descheduled while calibration
or, the check in PIT calibration may fail due to other virtualization
overheads.

The warning message explicitly assumes that calibration failed due to SMI's
which may not be the case. Change that to something proper.

Signed-off-by: Alok N Kataria <akataria@vmware.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>