x86, rdrand: When nordrand is specified, disable RDSEED as well

One can logically expect that when the user has specified "nordrand",
the user doesn't want any use of the CPU random number generator,
neither RDRAND nor RDSEED, so disable both.

Reported-by: Stephan Mueller <smueller@chronox.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Link: http://lkml.kernel.org/r/21542339.0lFnPSyGRS@myon.chronox.de


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>