sensors: fix the boot time warning of the cm36283 sensor sysfs

The sensor cm36283 sysfs ATTR ls_adc is read only ,so the permission
should be 0444 not 0664.

Change-Id: I2b9695cd8225785297778d5f9719e48983deb0a7
Signed-off-by: Jie Cheng <rockiec@codeaurora.org>