io_uring: enable io_mem_alloc/free to be used in other parts

stable inclusion
from stable-v6.6.5
commit 4ca5f54af7d3b60613991b201223c2dc6ebdf1c8
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8N21P

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4ca5f54af7d3b60613991b201223c2dc6ebdf1c8



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commit edecf1689768452ba1a64b7aaf3a47a817da651a upstream.

In preparation for using these helpers, make them non-static and add
them to our internal header.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>