remove redundant arg

So, in the original hcp modifications, there was this m_rcs2lai_nohalf variable... but the line that applied halfvox to m_rcs2lai was also commented out. Now the halfvox stuff only happens when use_hcp_siemens is false, and there never was any difference between m_rcs2lai and m_rcs2lai_nohalf.

So I renamed all _nohalf to remove the suffix, but didn't notice that the two were being redundantly passed into use_hcp_siemens.