NFSD: replace __get_free_page() with kmalloc() in nfsd_buffered_readdir()

NFSD: replace __get_free_page() with kmalloc() in nfsd_buffered_readdir()

nfsd_buffered_readdir() allocates a staging buffer with __get_free_page().

kmalloc() is a better API for such use and it also provides better
scalability and more debugging possibilities.

Replace use of __get_free_page() with kmalloc().

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://patch.msgid.link/20260523-b4-fs-v1-7-275e36a83f0e@kernel.org
Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>