Platform: Fix some build errors of lairdconnectivity

- Corrected typo and remove unused variable.
- Add tfm_hal_nvic.c to platform_s to use new interrupt HAL API.

Change-Id: I62170c2e21f669f9a9715e143177c68e3b05491d
Signed-off-by: Shawn Shan <Shawn.Shan@arm.com>
2 files changed