community/modemmanager: add patch to fix broadmobi modems

This patch was submitted upstream [1] but hasn't been merged yet. I'm submitting it separately since it fixes a nasty bug on the Librem 5 modem that causes the modem to enter a reset loop when USB bus power management is enabled (which is necessary to conserve energy).

1. https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/932

(cherry picked from commit af88f0be)