6593097586
* dahdi_registration writes multiple times to:
/sys/bus/astribanks/devices/*/*/span
* In some race cases this resulted in corruption and eventual kernel
panic.
* Until migration to "assigned-spans" is complete:
- Accept and ignore multiple "dahdi registrations" from user-space.
Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>