firmware: Add missing attributes to EFI variable attribute print out from sysfs

commit 7083909023bbe29b3176e92d2d089def1aa7aa1e upstream.

Some of the EFI variable attributes are missing from print out from
/sys/firmware/efi/vars/*/attributes. This patch adds those in. It also
updates code to use pre-defined constants for masking current value
of attributes.

Signed-off-by: Khalid Aziz <khalid.aziz@hp.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>