dt-bindings: display: add missing semicolon in example

Add missing semicolon in example for Sitronix ST7735R display panels.

Cc: Rob Herring <robh@kernel.org>
Cc: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Rob Herring <robh@kernel.org>