buildroot

ltp-testsuite: make Config.in libc comment standard

ltp-testsuite was the only package to mention "non-musl" while all other
packages have it as "glibc or uClibc". This change only adjusts it to
look like all the other packages.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>