intel_rng: make device not found a warning

Since many distros load this driver by default (throw it against the wall
and see what sticks method).  Change the error message severity level to
avoid alarming users.  Isn't it annoying when users actually read the
error logs...

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Cc: Michael Buesch <mb@bu3sch.de>
Acked-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>