Drop secure boot Kconfig symbols too
    
    Commit cc1db7f34788 ("Updates for secure boot") and commit 8e8de459e7ba
    ("Forgot to remove dropped patches") removed the patches that added
    Kconfig symbols EFI_SIGNATURE_LIST_PARSER and LOAD_UEFI_KEYS. Remove
    these symbols from the configuration generation directory and from the
    shipped .config files.
    
    Signed-off-by: Paul Bolle <pebolle@tiscali.nl>