mfd: tps65219: Add GPIO cell instance

TPS65219 PMIC GPIOs are exposed in a standard way:

  gpiodetect
  gpiochip0 [tps65219-gpio] (3 lines)

tps65219-gpios is incorrect cell name (plural).  Changed to
tps65219-gpio (singular)

Co-developed-by: Jonathan Cormier <jcormier@criticallink.com>
Signed-off-by: Jonathan Cormier <jcormier@criticallink.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jerome Neanne <jneanne@baylibre.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230511-tps65219-add-gpio-support-v5-2-ebb94281c854@baylibre.com