powerpc/85xx: fix definition of MAS register macros

Some of the MAS register macros do not protect the parameter with
parentheses, which could cause wrong values if the parameter includes
operators.

Also fix the definition of TSIZE_TO_BYTES() so that it actually uses
the parameter.  This hasn't caused any problems to date because the
parameter was always been 'tsize'.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>