i2c: i801: Use GPIO_LOOKUP() helper macro

i801_add_mux() fills in the GPIO lookup table by manually populating an
array of gpiod_lookup structures.  Use the existing GPIO_LOOKUP() helper
macro instead, to relax a dependency on the gpiod_lookup structure's
member names.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>