generic: convert crypto-ocf from kernel_thread to kthread

generic: convert crypto-ocf from kernel_thread to kthread

recent kernels have finally stopped exporting kernel_thread, since a
deprecation circa 2006.  This patch attempts to convert to the newer
kernel kthread API, particularly in random.c

[juhosg: remove randomproc variable, it is not required after the patch]

Signed-off-by: Russell Senior <russell@personaltelco.net>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35456 3c298f89-4303-0410-b956-a3cf2f4a3e73