Always use GL_CLAMP_TO_EDGE instead of GL_REPEAT, since OpenGL ES2
doesn't support NPOT textures in combination with GL_REPEAT by
default, and repeat is not needed anyway.

See also qtbase commits:
    8dfeb1c374972f06759a92b4edc5d6a18b96ccec
    8ab1323842433fb6b45e7d6f381b4b9710a81da9
    72558e810d9b3493dabfc936fa6c8bf3c3f3b49c

Change-Id: I01770fe3352da05baf6898d63c091bfae95e7a98
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>