mhi: dev: netdev: add debugfs hook to disable SKB chaining

Add debugfs entries to disable chaining of SKBs from MHI network
driver.

CRs-Fixed: 2482422
Change-Id: Ic8731fa293828a50245e5ea46d7770cd6703085c
Acked-by: Bhaumik Vasav Bhatt <bbhatt@qti.qualcomm.com>
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>