blockchain: Remove unneeded unspentness size check. (#665)
blockchain: Remove unneeded unspentness size check. (#665)

The current code is needlessly checking the number of bytes needed to
serialize the unspentness bitmap in the utxo against a maximum value
that could never be returned because the function takes a uint32 output
index which is treated as a bit offset, and converts it bytes, which
will necessarily be less than a max uint32.

This check also causes a compile error on arm where native integers are
32 bits.

This simply removes the unneeded check.
Stash-Crypto/btcd,ppcsuite/ppcd,BitGo/prova,davecgh/btcd,cqswxj2013/btcd,wallclockbuilder/btcd,jrick/btcd,ltcsuite/ltcd,decred/dcrd,tb00/btcd,aakselrod/btcd,jongillham/btcd,aakselrod/btcd,hectorj/btcd,jongillham/btcd,dajohi/btcd,adiabat/btcd,Roasbeef/btcd,jrick/dcrd,stevenroose/btcd,dajohi/btcd,adiabat/btcd,cqswxj2013/btcd,dajohi/btcd,BitGo/prova,Stash-Crypto/btcd,btcsuite/btcd,Roasbeef/btcd,jcmincke/dcrd,davecgh/btcd,wallclockbuilder/btcd,tb00/btcd,soapboxsys/ombfullnode,stevenroose/btcd,jcmincke/dcrd,hectorj/btcd,jrick/btcd,soapboxsys/ombfullnode,decred/dcrd,jrick/btcd,jrick/dcrd,jcmincke/dcrd,ppcsuite/ppcd,ltcsuite/ltcd,btcsuite/btcd