Revert "moglcore: Try to add rebinding of glGenerateMipmapOES() to make it work on OpenGL-ES."

This reverts commit e302f911fb27bbed5edc952b2af42ffc05740085.

That method didn't work out at all on Tegra. Turns out, proper
function was already bound, and the problem lies elsewhere,
so this didn't help but hurt!