toolchain: Add uClibc 0.9.30.3, remove older 0.9.30.x

As the 0.9.30.x stable releases only contain bugfixes, there isn't much
sense in using the older 0.9.30.x releases instead of .3, so use a single
0.9.30.x config similar to how we do it for the kernel headers.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>