UBUNTU: SAUCE: (efi-lockdown) MODSIGN: Fix module signature verification

UBUNTU: SAUCE: (efi-lockdown) MODSIGN: Fix module signature verification

BugLink: http://bugs.launchpad.net/bugs/1712168
Currently mod_verify_sig() calls verify_pkcs_7_signature() with
trusted_keys=NULL, which causes only the builtin keys to be used
to verify the signature. This breaks self-signing of modules with
a MOK, as the MOK is loaded into the secondary trusted keyring.
Fix this by passing the spacial value trusted_keys=(void *)1UL,
which tells verify_pkcs_7_signature() to use the secondary
keyring instead.

(cherry picked from commit cff4523d65b848f9c41c9e998a735ae2a820da2d
 git://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git)
[ saf: Taken from fedora commit without authorship information or much
  of a commit message; modified so that commit will describe the
  problem being fixed. ]
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>