dt-bindings: i2c: at91: fix i2c-sda-hold-time-ns documentation for sam9x60

SAM9X60 also supports i2c-sda-hold-time-ns. Fix the documentation accordingly.

Fixes: 2034e3f4 ("dt-bindings: i2c: at91: add new compatible")
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>