pinctrl: renesas: r8a779g0: Fix TPU suffixes

The Timer Pulse Unit channels have two alternate pin groups:
"tpu_to[0-3]" and "tpu_to[0-3]_a".

Increase uniformity by adopting R-Car V4M naming:
  - Rename "tpu_to[0-3]_a" to "tpu_to[0-3]_b",
  - Rename "tpu_to[0-3]" to "tpu_to[0-3]_a",

Fixes: ad9bb2fe ("pinctrl: renesas: Initial R8A779G0 (R-Car V4H) PFC support")
Fixes: 050442ae ("pinctrl: renesas: r8a779g0: Add pins, groups and functions")
Fixes: 85a9cbe4 ("pinctrl: renesas: r8a779g0: Add missing TPU0TOx_A")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/0dd9428bc24e97e1001ed3976b1cb98966f5e7e3.1717754960.git.geert+renesas@glider.be