vfio/ccw: remove unnecessary malloc alignment

Everything about this allocation is harder than necessary,
since the memory allocation is already aligned to our needs.
Break them apart for readability, instead of doing the
funky arithmetic.

Of the structures that are involved, only ch_ccw needs the
GFP_DMA flag, so the others can be allocated without it.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>