platform/x86: mlx-platform: Add support for new VMOD0007 board name

Add support for new Mellanox system type MSN3700C, which is
a cost reduced flavor of the MSN37 system class.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>