Fix invalid combinations for texture/copy on ES2 driver

Fix invalid combinations for texture/copy on ES2 driver

The OES_rgb8_rgba8 extension specification only specifies
RenderbufferStorageOES for additional GL_RGB8/GL_RGBA8 tokens.  ES3 spec
made these mandatory formats for texturing/copying.

Affects:

KHR-GLES2.core.internalformat.texture2d.rgb_unsigned_byte_rgb8
KHR-GLES2.core.internalformat.texture2d.rgba_unsigned_byte_rgb8
KHR-GLES2.core.internalformat.copy_tex_image.rgba8
KHR-GLES2.core.internalformat.copy_tex_image.rgb8

Components: OpenGL
VK-GL-CTS issue: 1260

Change-Id: Icbbd8882c5e623f5ac4725eebf977f535cfbfa31
(cherry picked from commit 5f7e621d6065f843651f7ca8f98989d05ca0bd65)