mptfusion: simplify rounding

Rounding up to a multiple of 4 should be done using the ALIGN
macro. As a bonus, this also makes the generated code smaller.

In GetIocFacts(), sz is assigned to a few lines below without being
read in the meantime, so it is ok that it doesn't end up with the same
value as facts->FWImageSize.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Joe Lawrence <joe.lawrence@stratus.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>