sysreset: select DM_GPIO instead of GPIO

CONFIG_GPIO does not exist. sysreset_gpio.c uses the DM gpio APIs so the
correct option to select is DM_GPIO.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>