bluez5_utils: gatttool depends on bluez5_utils client

bluez5_utils: gatttool depends on bluez5_utils client

The gatttool utility uses readline, and is therefore built only if
--enable-client is used, i.e when bluez5_utils client applications are
enabled. Therefore, this commit makes
BR2_PACKAGE_BLUEZ5_UTILS_GATTTOOL depend on
BR2_PACKAGE_BLUEZ5_UTILS_CLIENT. It also moves
BR2_PACKAGE_BLUEZ5_UTILS_GATTTOOL to be right below the
BR2_PACKAGE_BLUEZ5_UTILS_CLIENT definition.

Fixes:

  http://autobuild.buildroot.org/results/f2b/f2b8b1bf5d50e6223a9a6d6858320975edb2a25a/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>