vm_radix: eliminate reload in _remove

[dougm]

Summary

In the loop that searches for the last child, load that child once, without loading it again after the search is over. Change a comparison from ">= 1" to "!= 0". The two changes reduce code size by 32 bytes on amd64.

[dougm]

Drop the broken comparison change. Now, I can only save 16 bytes.

[alc]

sys/vm/vm_radix.c

782–784

Wouldn't it now make more sense to assert that tmp is not NULL?

[dougm]

Change asserts to check NULL.

sys/vm/vm_radix.c

782–784

Yes.