ARM: dts: omap3-devkit8000: fix a typo in GMPC node

"gpmc,sync-clki-ps" is not defined/documented, it should be
"gpmc,sync-clk-ps" instead.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Benoit Cousson <bcousson@baylibre.com>