nvmem: core: limit cell sysfs permissions to main attribute ones

nvmem: core: limit cell sysfs permissions to main attribute ones

The cell sysfs attribute should not provide more access to the nvmem
data than the main attribute itself.
For example if nvme_config::root_only was set, the cell attribute
would still provide read access to everybody.

Mask out permissions not available on the main attribute.

Fixes: 0331c611949f ("nvmem: core: Expose cells through sysfs")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240628113704.13742-5-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>