x86, cpufeature: Update CPU feature RDRND to RDRAND

The Intel manual changed the name of the CPUID bit to match the
instruction name. We should follow suit for sanity's sake. (See Intel SDM
Volume 2, Table 3-20 "Feature Information Returned in the ECX Register".)

[ hpa: we can only do this at this time because there are currently no CPUs
  with this feature on the market, hence this is pre-hardware enabling.
  However, Cc:'ing stable so that stable can present a consistent ABI. ]

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Link: http://lkml.kernel.org/r/20110524232926.GA27728@outflux.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: <stable@kernel.org> v2.6.36-39