pwm: Tidyup PWM menu for Renesas

Because current PWM Kconfig is sorting by symbol name,
it looks strange ordering in menuconfig.

=>	[ ]   Renesas R-Car PWM support
=>	[ ]   Renesas TPU PWM support
	[ ]   Rockchip PWM support
=>	[ ]   Renesas RZ/G2L General PWM Timer support
=>	[ ]   Renesas RZ/G2L MTU3a PWM Timer support

Let's use common CONFIG_PWM_RENESAS_xxx symbol name for Renesas,
and sort it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/877c2mxrrr.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>