zsmalloc: use all available 24 bits of page_type

zsmalloc: use all available 24 bits of page_type

Now that we have an extra 8 bits, we don't need to limit ourselves to
supporting a 64KiB page size.  I'm sure both Hexagon users are grateful,
but it does reduce complexity a little.  We can also remove
reset_first_obj_offset() as calling __ClearPageZsmalloc() will now reset
all 32 bits of page_type.

Link: https://lkml.kernel.org/r/20240821173914.2270383-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>