ipc4: remove needless interrupt disabling

[lyakh]

ipc4_get_drv() is called from ipc4_get_comp_drv() in IPC context, and that can run on different cores, so just disabling local interrupts doesn't provide proper protection. On the other hand IPCs are serialised, and the global driver list can only be modified from IPC context, so there is no need to protect it here. Remove the interrupt lock.