maple_tree: Remove MA_STATE_PREALLOC

maple_tree: Remove MA_STATE_PREALLOC

MA_SATE_PREALLOC was added to catch any writes that try to allocate when
the maple state is being used in preallocation mode.  This can safely be
removed in favour of the percpu array of nodes.

Note that mas_expected_entries() still expects no allocations during
operation and so MA_STATE_BULK can be used in place of preallocations
for this case, which is primarily used for forking.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>