dt-bindings: pwm: remove Xinlei's mail

Xinlei Lee's mail is bouncing:

<xinlei.lee@mediatek.com>: host mailgw02.mediatek.com[216.200.240.185] said:
    550 Relaying mail to xinlei.lee@mediatek.com is not allowed (in reply to
    RCPT TO command)

Remove it.

Signed-off-by: Michael Walle <mwalle@kernel.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>