Make some unwise casts. On i386 these casts wind up being safe. Rather
than disturb the API, go with these casts to shut gcc up.
Make this compile with gcc.

Submitted by: royger@
Make the vmm code compile with gcc too. Not entirely sure things are
correct for the pirbase test (since I'd have thought we'd need to do
something even when the offset is 0 and that test looks like a
misguided attempt to not use an uninitialized variable), but it is at
least the same as today.
Follow files.imx51 and add vt support.
Add fsl,imx53.
Need to include machine/fdt.h.