wavpack: fix the iconv breakage ghost

Fix missing comma in DEPENDENCIES, causing to pull in libiconv when it
wasn't necessary and causing other packages to go crazy on (e)glibc
toolchains which don't need it with libiconv being present. Fixes:
http://autobuild.buildroot.org/results/e0ce086a33a1db6fee77f43356e4e94ed6941f17



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>