ARM: dts: OMAP5+: Enable gpio in SPL

gpio2 is used to detect lcd based on which pin mux is done in SPL.
gpio7 is used to enable vtt regulator. Enable these two gpio nodes
in SPL.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>