hwmon: (nct6775) Use int type to store negative error codes

hwmon: (nct6775) Use int type to store negative error codes

Change the 'ret' variable from u32 to int in nct6775_asuswmi_read() to
store negative error codes or zero;

Storing the negative error codes in unsigned type, doesn't cause an issue
at runtime but can be confusing. Additionally, assigning negative error
codes to unsigned type may trigger a GCC warning when the -Wsign-conversion
flag is enabled.

No effect on runtime.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Link: https://lore.kernel.org/r/20250830095105.3271-1-rongqianfeng@vivo.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>