ifdtool: Makefile: fix install target

ifdtool doesn't have a manual yet, so don't install
an unexisting manual file.

Change-Id: I290435de7de7177d803cf6cde4f4f42955cbcf5c
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
Reviewed-on: http://review.coreboot.org/12406
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
1 file changed