FROMLIST: BACKPORT: maple_tree: Refine mas_preallocate() node calculations

Calculate the number of nodes based on the pending write action instead
of assuming the worst case.

This addresses a performance regression introduced in platforms that
have longer allocation timing.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>

Link: https://lore.kernel.org/all/20230612203953.2093911-15-Liam.Howlett@oracle.com/


[surenb: replace mas_wr_new_end with mas_wr_node_size]

Bug: 274059236
Change-Id: I8fc22bca45fa005acf767722034a260242a4da52
Signed-off-by: Suren Baghdasaryan <surenb@google.com>