RDMA/mlx5: reduce stack usage in mlx5_ib_ufile_hw_cleanup

RDMA/mlx5: reduce stack usage in mlx5_ib_ufile_hw_cleanup

This function has an array of eight mlx5_async_cmd structures, which
often fits on the stack, but depending on the configuration can
end up blowing the stack frame warning limit:

drivers/infiniband/hw/mlx5/devx.c:2670:6: error: stack frame size (1392) exceeds limit (1280) in 'mlx5_ib_ufile_hw_cleanup' [-Werror,-Wframe-larger-than]

Change this to a dynamic allocation instead. While a kmalloc()
can theoretically fail, a GFP_KERNEL allocation under a page will
block until memory has been freed up, so in the worst case, this
only adds extra time in an already constrained environment.

Fixes: 7c891a4dbcc1 ("RDMA/mlx5: Add implementation for ufile_hw_cleanup device operation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20250610092846.2642535-1-arnd@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>