soc/amd/common/block/gpio_banks/gpio: add comment in check_gpios

Each bit in the GPIO wake status index registers is set to 1 when at
least one of 4 corresponding GPIO pins has its wake status register set.
Added the comment since the gpio_base + i * 4 in the next line looked as
if it calculates some absolute register value which is not what the code
does or should be doing.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I2fc8e9c5bd7c1b011f364b05d0cfdeb0df88ada6
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56703
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/common/block/gpio_banks/gpio.c

@@ -308,6 +308,7 @@ static void check_gpios(uint32_t wake_stat, int bit_limit, int gpio_base,
 	for (i = 0; i < bit_limit; i++) {
 		if (!(wake_stat & BIT(i)))
 			continue;
+		/* Each wake status register bit is for 4 GPIOs that then will be checked */
 		begin = gpio_base + i * 4;
 		end = begin + 4;
 		/* There is no gpio 63. */