samples/net: Remove redundant configuration variable Remove CONFIG_GPIO=y for the Arduino 101 board. This configuration is now set by default in the board configuration file. See commit 8f96628064475ed34288ed0583a881835b666501. Change-Id: I6fa73a5785d78c51f03a0af48fc2aa8cc7636c7d Signed-off-by: Flavio Santes <flavio.santes@intel.com>