samples: mgmt: osdp: Fix compile issue

With the change to use GPIO_DT_SPEC_GET_OR a number of platforms
failed to build these samples.  This was due to the GPIO drivers not
being enabled by default.  Add CONFIG_GPIO=y to the prj.conf to fix
the issue.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
2 files changed