hwrng: Move UML_RANDOM at the last position

UML_RANDOM is the only hardware random number generator option which
does not depend on HW_RANDOM. Having it in the middle of the other
options breaks the alignment in "make menuconfig". Move it at the last
position to avoid that.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>