pinctrl: renesas: r8a779g0: FIX PWM suffixes

PWM channels 0, 2, 8, and 9 do not have alternate pins.
Remove their "_a" or "_b" suffixes to increase uniformity.

Fixes: c606c2fd ("pinctrl: renesas: r8a779g0: Add missing PWM")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/abb748e6e1e4e7d78beac7d96e7a0a3481b32e75.1717754960.git.geert+renesas@glider.be