dt-bindings: timer: renesas,rz-mtu3: Fix overflow/underflow interrupt names

As per R01UH0914EJ0130 Rev.1.30 HW manual the MTU3 overflow/underflow
interrupt names starts with 'tci' instead of 'tgi'.

Fix this documentation issue by replacing below overflow/underflow
interrupt names:
 - tgiv0->tciv0
 - tgiv1->tciv1
 - tgiu1->tciu1
 - tgiv2->tciv2
 - tgiu2->tciu2
 - tgiv3->tciv3
 - tgiv4->tciv4
 - tgiv6->tciv6
 - tgiv7->tciv7
 - tgiv8->tciv8
 - tgiu8->tciu8

Fixes: 0a9d6b54 ("dt-bindings: timer: Document RZ/G2L MTU3a bindings")
Cc: stable@kernel.org
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230727081848.100834-2-biju.das.jz@bp.renesas.com