aufs: linux-v5.10-rc1, no more f_op->read() and ->write()

By the previous commit,
	51958525b3fd9 2020-12-22 for aufs: linux-v5.10-rc1, no more vfs_(read|write)f_t
f_op->read() and ->write() are less meaningful.
Now aufs totally removes them.

Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
(cherry picked from commit 2254d10ddd118d7581ac8d401cd80b839a7b43ed
 in https://github.com/sfjro/aufs5-linux)
Signed-off-by: Vefa Bicakci <vefa.bicakci@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>