linux-samsung-coreprimevelte: upgrade to v6.7-rc7

This MR fixes a regression in !4650 (merged) where enabling CONFIG_USB_CONFIGFS_NCM caused USB networking to stop working (specifically, my PC would get an IP address, but the phone wouldn't).

Besides that, I have fixed an ancient oversight regarding the modem reserved memory. This frees up 32MB of memory, which is rather sizeable considering the phone only has 1GB.