Revert "isdn: mISDN: Fix potential NULL pointer dereference of kzalloc"

Revert "isdn: mISDN: Fix potential NULL pointer dereference of kzalloc"

This reverts commit 38d22659803a033b1b66cd2624c33570c0dde77d.

Because of recent interactions with developers from @umn.edu, all
commits from them have been recently re-reviewed to ensure if they were
correct or not.

Upon review, this commit was found to be incorrect for the reasons
below, so it must be reverted.  It will be fixed up "correctly" in a
later kernel change.

While it looks like the original change is correct, it is not, as none
of the setup actually happens, and the error value is not propagated
upwards.

Cc: Aditya Pakki <pakki001@umn.edu>
Cc: David S. Miller <davem@davemloft.net>
Link: https://lore.kernel.org/r/20210503115736.2104747-47-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>