arm: curie_ble: Report curie_ble as a unique board

CONFIG_BOARD was set to arduino_101_ble instead of curie_ble.  Fix this
so the BOARD_NAME, BOARD, board dir, all are in sync.

Change-Id: I5f2a4f1aeec7c20f042e11b96e1c87883ad4df4b
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>