usb: gadget: mbim: Update bNumberFilters to 32

MBIM specification requires mbim maximum
packet filters value to be 32.
This changes sets bNumberFilters field of the
USB MBIM Functional Descriptor,
specifying maximum packet filters value,
to be 32.

CRs-Fixed: 423389
Change-Id: Ieab57de0502a553f63b08a0d6e947178bfc12e2d
Signed-off-by: Anna Perel <aperel@codeaurora.org>