ARM: dts: omap: fix gpmc,mux-add-data type

gpmc,mux-add-data is not boolean.

Fixes the below errors flagged by dtbs_check.

"ethernet@4,0:gpmc,mux-add-data: True is not of type 'array'"

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>