[x86] Remove CLWB from cannonlake.

[Koval, Julia]

In latest ISE extensions document 
https://software.intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-reference.pdf
 CLWB was removed from Cannonlake. This patch removes it from GCC. Ok for trunk?

Thanks,
Julia

gcc/
        * config/i386/i386.c (ix86_option_override_internal): Remove PTA_CLWB 
from
        PTA_CANNONLAKE.

patch
Description: patch