package/Makefile.in: Fix dependency for selecting uclinux as TARGET_OS

Current setting only allows blackfin to select uclinux as TARGET_OS.
However, some noMMU ARM platforms that using FLAT binary format also need to
select uclinux as TARGET_OS. Fix the dependency.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>