package/kernel: create separate package for the sha256 crypto module

Based on a patch from #12711

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@34955 3c298f89-4303-0410-b956-a3cf2f4a3e73
package/kernel: select crypto-sha256 for cifs on 3.7+

Based on a patch from #12711

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@34956 3c298f89-4303-0410-b956-a3cf2f4a3e73