hwmon: (lenovo-ec-sensors): Fix EC "MCHP" signature validation logic

hwmon: (lenovo-ec-sensors): Fix EC "MCHP" signature validation logic

The EC signature check uses && instead of || between the four
byte comparisons.  With &&, the condition is true only when ALL
four bytes fail to match simultaneously, meaning the driver
accepts a device as a valid Microchip EC if ANY single byte of
the 4-byte "MCHP" signature happens to match.

Due to short-circuit evaluation, if the first byte reads back as
'M' (0x4D, a very common register value), the remaining three
comparisons are skipped entirely and the device is accepted.

Change && to || so the check rejects devices that do not fully
match the expected EC signature, as originally intended.

Fixes: 70118f85e6538 ("hwmon: Add EC Chip driver for Lenovo ThinkStation motherboards")
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Signed-off-by: Kean Ren <rh_king@163.com>
Link: https://lore.kernel.org/r/20260521035228.533317-3-rh_king@163.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>