pwm: mediatek: Simplify representation of channel offsets

pwm: mediatek: Simplify representation of channel offsets

The general register layout contains some per-chip registers starting at
offset 0 and then at a higher address there are n nearly identical and
equidistant blocks for the registers of the n channels.

This allows to represent the offsets of per-channel registers as $base +
i * $width instead of listing all (or too many) offsets explicitly in an
array. So for a small additional effort in pwm_mediatek_writel() the
three arrays with the channel offsets can be dropped.

The size changes according to bloat-o-meter are:

	add/remove: 0/3 grow/shrink: 1/0 up/down: 12/-96 (-84)
	Function                                     old     new   delta
	pwm_mediatek_apply                           696     708     +12
	mtk_pwm_reg_offset_v3                         32       -     -32
	mtk_pwm_reg_offset_v2                         32       -     -32
	mtk_pwm_reg_offset_v1                         32       -     -32
	Total: Before=5347, After=5263, chg -1.57%

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20250725154506.2610172-11-u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>