Adjust #if statements inside mprsas_send_smpcmd() to more accurately
reflect when unmapped I/O support was added.

For FreeBSD 10, it arrived just prior to FreeBSD_version 1000028.
For FreeBSD 9, it arrived just prior to FreeBSD_version 902001.

Also, fix compiler warnings in mprsas_send_smpcmd() that happen in the
i386 PAE build for non-unmapped I/O builds. These were fixed in mps(4)
in revision 241145, but didn't make it into the mpr(4) driver. This
change should only affect FreeBSD versions outside the above revisions,
and thus doesn't affect head.

MFC after: 3 days
Sponsored by: Spectra Logic Corporation