pinctrl: renesas: r8a7791: Remove INTC_IRQx_N

The INTC_IRQx_N pin functions were only documented in preliminary
versions of the R-Car M2 Hardware User's Manual, and were never used.

This reduces kernel size by 40 bytes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/932834b388887e1ae267e5a852c688c79091a5f9.1640269369.git.geert+renesas@glider.be