hwrng: core - Convert sprintf/snprintf to sysfs_emit

Per filesystems/sysfs.rst, show() should only use sysfs_emit()
or sysfs_emit_at() when formatting the value to be returned to user space.

coccinelle complains that there are still a couple of functions that use
snprintf(). Convert them to sysfs_emit().

sprintf() will be converted as weel if they have.

Generally, this patch is generated by
make coccicheck M=<path/to/file> MODE=patch \
COCCI=scripts/coccinelle/api/device_attr_show.cocci

No functional change intended

CC: Olivia Mackall <olivia@selenic.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: linux-crypto@vger.kernel.org
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>