Mem: Reclaim some request flags used by MIPS for alignment checking.

Mem: Reclaim some request flags used by MIPS for alignment checking.

These flags were being used to identify what alignment a request needed, but
the same information is available using the request size. This change also
eliminates the isMisaligned function. If more complicated alignment checks are
needed, they can be signaled using the ASI_BITS space in the flags vector like
is currently done with ARM.