drivers: input: npcx: init semaphore before interrupt enable

A kernel panic was observed on a platform when k_sem_give() was called
in npcx_kbd_ksi_isr(). From the panic information, it appears that
the semaphore was used before it was initialized. This commit prevents
the potential issue by enabling the interrupt only after
the input_kbd_matrix_common_init() function is called
(where the semaphore is initialized).

Signed-off-by: Jun Lin <CHLin56@nuvoton.com>