package/kmsxx: detect failure at install-staging

Currently, the staging-install commands do not detect failures to
install the libs.

That's because we use ';' to separate the commands, so we only get the
result of the last one.

Fix that by using multi-line commands, so they each are called on their
own and make would catch the failures.

Partially fixes (only detects the real failure):
    http://autobuild.buildroot.org/results/82c/82cfb7451f933b222abe30b5d35d23e409a4af79


    and a few others.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>