Chunks are 256KB, so use constants for the size/shift/mask, rather than
getting them from the msChunks struct. The iSeries debugger (??) might still
need access to the values in the msChunks struct, so we keep them around
for now, but set them from the constant values.

Replace msChunks_entry typedef with regular u32.

Simplify msChunks_alloc() to manipulate klimit directly, rather than via
a parameter.

Move msChunks_alloc() and msChunks into iSeries_setup.c, as that's where
they're used.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>