digsig: remove redefinition of __ATTR macro

__ATTR is already defined in linux/sysfs.h, so it doesn't need to be
redefined further on.

Signed-off-by: Rupert Muchembled <rupert@rmuch.net>
digsig: remove DIGSIG_LTM conditional

LTM sources have been removed in a previous commit, keeping this ifdef
is unnecessary.

Signed-off-by: Rupert Muchembled <rupert@rmuch.net>