Smack: use select not depends in Kconfig

Smack: use select not depends in Kconfig

The components NETLABEL and SECURITY_NETWORK are required by
Smack. Using "depends" in Kconfig hides the Smack option
if the user hasn't figured out that they need to be enabled
while using make menuconfig. Using select is a better choice.
Because select is not recursive depends on NET and SECURITY
are added. The reflects similar usage in TOMOYO and AppArmor.

Targeted for git://git.gitorious.org/smack-next/kernel.git

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>