gconf: Disable gtk support

gconf: Disable gtk support

There are only a couple of helper utilities within gconf that need gtk+ as a
dependency and those are unused and pretty useless. We might as well drop
the dependency on gtk and allow more parallel builds by reducing dependency
bottlenecks.

(From OE-Core rev: 6facee8443966b646cd1e72f14ae13e58a13f621)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>