bus: mhi: host: pci_generic: Fix the modem name of Foxconn T99W640

T99W640 was mistakenly mentioned as T99W515. T99W515 is a LGA device, not
a M.2 modem device. So correct it's name to avoid name mismatch issue.

Fixes: bf30a75e ("bus: mhi: host: Add support for Foxconn SDX72 modems")
Signed-off-by: Slark Xiao <slark_xiao@163.com>
[mani: commit message fixup]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20250606095019.383992-1-slark_xiao@163.com