Rev.0.81 of the R-Car V4M Series Hardware User’s Manual removed the
"STPWT_EXTFXR" signal from the pin control register tables. As this is
further unused in the pin control driver, it can be removed safely.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>