msm: mhi_rmnet: add support for dynamic interface name

mhi_rmnet support both hardware accelerated path,
and software path for IP traffic. Add support to
configure interface name through device tree.

CRs-Fixed: 2022229
Change-Id: I8356c599ce22ae45e0f3c03272ebf50251a73a59
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>