msm: mhi_dev: add random mac generation and ethernet parse support

Host can generate Ethernet packets over the network stack. Add
support to assign proper protocol for ethernet packets. Also, add
support for mhi net device for random mac address generation.

Change-Id: Icd29e7df9aff0529ebaf4897560d9a9acec76fd7
Signed-off-by: Rama Krishna Phani A <rphani@codeaurora.org>