device: sdm845-{enchilada,fajita,axolotl}: rename qcom_spmi_fg to qcom_fg

kind of RFC: the deviceinfos for (sdm845) fajita, enchilada and axolotl all reference the qcom_spmi_fg module, which seems to have been renamed to qcom_fg?

axolotl additionally mentions an smb2 driver. beryllium otoh mentions no fg driver at all...

I've only literally replaced s/qcom_spmi_fg/qcom_fg/g, not looked at every sdm845 device to make sure they're even.

sdl-charging is gone anyway, do we want/need to keep these in the initramfs regardless?