Kconfig: enable CONFIG_CIFS_SMB2
    
    Enough of the CIFS SMB2 code has been merged into 3.7 that users can
    now mount SMB2.1 shares from servers that support it. It's still fairly
    experimental, but enabling the Kconfig option is unlikely to break
    users who are using SMB1.
    
    Let's go ahead and enable this in 3.7 kernels. I think this patch
    should be sufficient, but let me know if we should do anything else.
    
    Signed-off-by: Jeff Layton <jlayton@redhat.com>