nvme: fix namespace removal list

This function wants to move a subset of a list from one element to the
tail into another list. It also needs to use the srcu synchronize
instead of the regular rcu version. Do this one element at a time
because that's the only to do it.

Fixes: be647e2c

 ("nvme: use srcu for iterating namespace list")
Reported-by: Venkat Rao Bagalkote <venkat88@linux.vnet.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.vnet.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>