These options were only needed for a MyNewt-based nRF51 firmware on
these boards (the MyNewt BLE stack is called Nimble, hence the
prj_nimble.conf sample config files). With a Zephyr-based nRF51
firmware these options are no-longer needed, so it's not appropriate
to have them default to enabled. Instead, if they are needed, require
the app-specific configuration to enable them.
Change-Id: Iefbee4d97590af4e11bcedea05fe61f32a147b83
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>