bus: mhi: host: pci_generic: Add Foxconn T99W696 modem

T99W696 modem is based on Qualcomm SDX61 chipset, which is an economic
version compared to the baseline SDX62/SDX65 chipsets. Add support for it
by introducing a new 'mhi_channel_config'. Since this modem supports the
NMEA channel, a new config is needed.

Signed-off-by: Slark Xiao <slark_xiao@163.com>
[mani: reworded commit message]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20250528092232.16111-1-slark_xiao@163.com