PCI: Remove unnecessary "if" statement

In store_remove_id(), set the default return value to -ENODEV, and
overwrite it with the input buffer size if we find a matching list entry.
Then we don't need to test whether to return an error or the count.

No functional change.

[bhelgaas: changelog]
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>