i2c: i801: Use match_string() helper to simplify the code

match_string() returns the array index of a matching string.
Use it instead of the open-coded implementation.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>