mhi: dev: netdev: rename alias to mhi-netdev

As underscore in alias names is not allowed, rename alias
from mhi_netdev to mhi-netdev.

CRs-Fixed: 2385821
Change-Id: Iecad52ff3757ab4ba3e24858d936d95a538207a8
Acked-by: Bhaumik Vasav Bhatt <bbhatt@qti.qualcomm.com>
Signed-off-by: Tony Truong <truong@codeaurora.org>
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>