drivers: gpio: esp32: correct comment about pin drive strength

The comment about which drive strength option is high or low was
wrong and this commit fixes it. For example, ESP32_GPIO_DS_ALT
results in GPIO_DRIVE_CAP_0 being used which is the weakest
option according to the HAL file espressif-esp32-gpio.h.

Signed-off-by: Hein Wessels <heinwessels93@gmail.com>