UP2 with nocodec: oops on module remove/insert

[plbossart]

With the nocodec topology, the existing code generates an oops on insert. It looks like the cleanups are not done right with race conditions and sysfs entries inconsistent. The patch in #255 solves these issues by adding a second unregistration of the machine driver - which works but makes absolutely no sense... Clearly a timing issue that needs to be handled with a proper fix.

dmesg_before_remove.log
dmesg_after_remove.log
dmesg_after_insert.log

[plbossart]

Additional traces show the oops happens on insert - the machine driver is not created and the topology is freed before being created. So the root cause is why the machine driver is not created
and the error w/ sysfs: cannot create duplicate filename '/bus/platform/devices/sof-nocodec'

[plbossart]

this is getting beyond my understanding. We are looking at a bad link in sysfs, likely because of a removal done in the wrong order

lrwxrwxrwx 1 root root 0 Nov  8 20:08 /sys/bus/platform/devices/sof-nocodec -> ../../../devices/pci0000:00/0000:00:0e.0/sof-audio/sof-nocodec
root@ubilinux4:~# 
root@ubilinux4:~# 
root@ubilinux4:~# ls /sys/bus/devices/pci0000:00/0000:00:0e.0/sof* 
ls: cannot access '/sys/bus/devices/pci0000:00/0000:00:0e.0/sof*': No such file or directory

[plbossart]

Solved by unregistering the machine platform device from the SOF core, updated #255