ti-gfx.mk: correct typo

There is a simple typo in package/ti-gfx/ti-gfx.mk, which the
following patch corrects.

Signed-off-by: Martin Creutziger <buildroot@martin.creutziger.net>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/ti-gfx/ti-gfx.mk

@@ -29,7 +29,7 @@ TI_GFX_OMAPES = 5.x
 TI_GFX_PLATFORM = omap3630
 endif
 ifeq ($(BR2_PACKAGE_TI_GFX_ES6),y)
-TI_GFX_OMPAES = 6.x
+TI_GFX_OMAPES = 6.x
 TI_GFX_PLATFORM = ti81xx
 endif
 ifeq ($(BR2_PACKAGE_TI_GFX_ES8),y)