arm64: dts: uniphier: fix widget name of headphone for LD11/LD20 boards

This patch fixes wrong name of headphone widget for receiving events
of insert/remove headphone plug from simple-card or audio-graph-card.

If we use wrong widget name then we get warning messages such as
"asoc-audio-graph-card sound: ASoC: DAPM unknown pin Headphones"
when the plug is inserted or removed from headphone jack.

Fixes: fb21a0ac

 ("arm64: dts: uniphier: add sound node")
Signed-off-by: Katsuhiro Suzuki <suzuki.katsuhiro@socionext.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>