module: Remove double spaces in module verification taint message

The warning message when loading modules with a wrong signature has
two spaces in it:

"module verification failed: signature and/or  required key missing"

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --cc kernel/module.c
Simple merge