msm: mhi-net-dev: Set MIN and MAX MTU size for Ethernet packet

Set MIN and MAX MTU for ethernet packets, so the user can
configure MTU size. The default MTU size for the ethernet packet
is 1500 bytes. With this change, the user/client can update the
max MTU size up to 8192 (MHI_NET_DEFAULT_MTU) bytes.

Change-Id: I7da6d11599bde1a6d3a9ac9b238a4ee57a7bbbba
Signed-off-by: Veerabhadrarao Badiganti <quic_vbadigan@quicinc.com>
Signed-off-by: Sai Chaitanya Kaveti <quic_skaveti@quicinc.com>