x86, cpufeature: Add the RDSEED and ADX features

Add the RDSEED and ADX features documented in section 9.1 of the Intel
Architecture Instruction Set Extensions Programming Reference,
document 319433, version 013b, available from
http://software.intel.com/en-us/avx/

The PREFETCHW bit is already supported in Linux under the name
3DNOWPREFETCH.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/n/tip-lgr6482ufk1bvxzvc2hr8qbp@git.kernel.org