scripts/Makefile.lib: remove overridden target $(obj)/helloworld.so:

The target
$(obj)/helloworld.so:
exists twice in Makefile.lib.

If you add an echo command to each of the two recipes you get
warnings like:

scripts/Makefile.lib:383: warning:
overriding recipe for target 'drivers/power/battery/helloworld.so'
scripts/Makefile.lib:379: warning:
ignoring old recipe for target 'drivers/power/battery/helloworld.so'

This patch removes the obsolete target.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>