pinctrl: renesas: r8a779h0: Fix IRQ suffixes

The suffixes of the IRQ identifiers, as used for pins related to the
Interrupt Controller for External Devices (INTC-EX), are inconsistent.
Correct them to match the Pin Multiplex attachment in Rev.0.51 of the
R-Car V4M Series Hardware User's Manual.

Fixes: 291f7856 ("pinctrl: renesas: Initial R8A779H0 (R-Car V4M) PFC support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/7d3c7498d9e8eda5583b15f9163eb25bb797ed24.1713282028.git.geert+renesas@glider.be