gpio: mockup: Fix mode of debugfs files

stable inclusion
from stable-v5.10.181
commit ea50ee0ef9040e87e21165374aa553f410011536
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8GJZJ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ea50ee0ef9040e87e21165374aa553f410011536



--------------------------------

commit 0a1bb16e upstream.

This driver's debugfs files have had a read operation since commit
2a9e2740 ("gpio: mockup: rework debugfs interface"), but were
still being created with write-only mode bits.  Update them to
indicate that the files can also be read.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Fixes: 2a9e2740 ("gpio: mockup: rework debugfs interface")
Cc: stable@kernel.org # v5.1+
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>