jbd2: replace __get_free_pages() with kmalloc()

jbd2: replace __get_free_pages() with kmalloc()

jbd2_alloc() falls back from kmem_cache_alloc() to __get_free_pages() for
allocations larger than PAGE_SIZE.
But kmalloc() can handle such cases with essentially the same fallback.

Replace use of __get_free_pages() with kmalloc() and simplify
jbd2_free() as both kmem_cache_alloc() and kmalloc() allocations can be
freed with kfree().

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://patch.msgid.link/20260523-b4-fs-v1-10-275e36a83f0e@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>