hwmon: (stts751) Use permission specific SENSOR[_DEVICE]_ATTR variants

Use SENSOR[_DEVICE]_ATTR[_2]_{RO,RW,WO} to simplify the source code,
to improve readability, and to reduce the chance of inconsistencies.

Also replace any remaining S_<PERMS> in the driver with octal values.

The conversion was done automatically with coccinelle. The semantic patches
and the scripts used to generate this commit log are available at
https://github.com/groeck/coccinelle-patches/hwmon/

.

This patch does not introduce functional changes. It was verified by
compiling the old and new files and comparing text and data sizes.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>