pinctrl: rza2: Fix gpio name typos

Fix apparent copy/paste errors that were overlooked in the original driver.
  "P0_4" -> "PF_4"
  "P0_3" -> "PG_3"

Fixes: b59d0e78

 ("pinctrl: Add RZ/A2 pin and gpio controller")
Cc: <stable@vger.kernel.org>
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Link: https://lore.kernel.org/r/20190930145804.30497-1-chris.brandt@renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>