spi: dt-bindings: Fix description mentioning a removed property

spi: dt-bindings: Fix description mentioning a removed property

'spi-cpha' was removed from this file. So, replace it in the description
with an existing example. Reformat the paragraph to adhere to max line
length.

Fixes: 233363aba72a ("spi/panel: dt-bindings: drop CPHA and CPOL from common properties")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://patch.msgid.link/20250417111630.53084-2-wsa+renesas@sang-engineering.com
Signed-off-by: Mark Brown <broonie@kernel.org>