To make dell_micmute_led_set() work properly we need to ensure that either WMI
or SMM driver is already loaded and initialized.
From the looks of the call trace dell_micmute_led_set() is called from device
phase of initialization. Which means that there is a use of dell-laptop
interface while the module is not initialized (since late_initcall).
Previously, this led to crashes.
But dell_micmute_led_set() does not touch the module state now, so nothing is
technically broken; dell-smbios and dell-smbios-smm use subsys_initcall, so
they are ready. But WMI driver is in the same phase with intel hda, so there
might be something there.