First check if there is an alias for the device tree node defined with the
given num before checking against device index.

Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>