random: Fix handing of arch_get_random_long in get_random_bytes()

If there is an architecture-specific random number generator we use
it to acquire randomness one "long" at a time. We should put these
random words into consecutive words in the result buffer - not just
overwrite the first word again and again.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/4ec4061010261a4cb0@agluck-desktop.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>