hwmon: (pmbus/adm1266) reject implausible blackbox record_count

hwmon: (pmbus/adm1266) reject implausible blackbox record_count

adm1266_nvmem_read_blackbox() loops over a record_count that comes
straight from byte 3 of the BLACKBOX_INFO response.  The destination
buffer is data->dev_mem, sized for the nvmem cell's declared 2048
bytes (ADM1266_BLACKBOX_MAX_RECORDS * ADM1266_BLACKBOX_SIZE = 32 * 64).
A device that reports a record_count greater than 32 -- whether due
to firmware bugs, bus corruption, or a non-responsive slave returning
0xff -- would walk read_buff past the end of the dev_mem allocation
on the trailing iterations.

Cap record_count at ADM1266_BLACKBOX_MAX_RECORDS (introduced here)
before entering the loop and return -EIO on any larger value, so a
malformed BLACKBOX_INFO response cannot drive the loop out of bounds.

Fixes: 15609d189302 ("hwmon: (pmbus/adm1266) read blackbox")
Cc: stable@vger.kernel.org
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
Link: https://lore.kernel.org/r/20260515-adm1266-fixes-v1-3-1c1ea1349cfe@nexthop.ai
Signed-off-by: Guenter Roeck <linux@roeck-us.net>