Revert "modsign: Abort modules_install when signing fails"

This reverts commit caf6fe91.

The commit was fine but is no longer needed as of commit 3a2429e1
("kbuild: change if_changed_rule for multi-line recipe").  Let's go
back to using ";" to be consistent.

For some discussion, see:

https://lkml.kernel.org/r/CAK7LNASde0Q9S5GKeQiWhArfER4S4wL1=R_FW8q0++_X3T5=hQ@mail.gmail.com



Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>