buildroot

ccache: remove deprecated target package

The ccache target package has been deprecated since 2013.02 and thus can be
removed in 2014.02. This does not change anything about host ccache (used
for speeding up builds).

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>