hwmon: (fam15h_power) Add bit masking for tdp_limit

Add bit masking to read ApmTdpLimit precisely

Signed-off-by: Gioh Kim <gi-oh.kim@profitbricks.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>