lib/alloc: replace areas with more generic flags

Replace the areas parameter with a more generic flags parameter. This
allows for up to 16 allocation areas and 16 allocation flags.

This patch introduces the flags and changes the names of the funcions,
subsequent patches will actually wire up the flags to do something.

The first two flags introduced are:
- FLAG_DONTZERO to ask the allocated memory not to be zeroed
- FLAG_FRESH to indicate that the allocated memory should have not been
  touched (READ or written to) in any way since boot.

This patch also fixes the order of arguments to consistently have alignment
first and then size, thereby fixing a bug where the two values would get
swapped.

Fixes: 8131e91a ("lib/alloc_page: complete rewrite of the page allocator")

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Message-Id: <20210115123730.381612-10-imbrenda@linux.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>