Allocated blocks should keep rounded size

[tannewt]

I found a bug with the mattconte implementation that is in this implementation as well. https://github.com/espressif/tlsf/pull/2

Basically, allocated blocks need to be the rounded size so that they get freed to the same place they were searched for first. Otherwise, you may not be able to free a block and then re-allocate to the same location even if the sizes are the same.