usb: gadget: mbim: Set wMaxSegmentSize to 4064

According to the specification max_segment_size must be
at least 2048. To allow adding additional bytes to
ethernet frame based on ntb_out_max_size = 4094,
max_segment_size must be smaller than ntb_out_max_size.

Change-Id: Id3b9ef7c834f94f16d2fef238671c38038951a1f
CRs-Fixed: 362693
Signed-off-by: Anna Perel <aperel@codeaurora.org>