pinctrl: renesas: r8a7790: Remove INTC_IRQx_N

The INTC_IRQx_N pin functions were only documented in preliminary
versions of the R-Car H2 Hardware User's Manual, and were never used.

This reduces kernel size by 40 bytes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/5b3fb0c025eaca037a53120fee811cf13e08b55f.1640269218.git.geert+renesas@glider.be