Refix invalid glTexImage2D operation in FramebufferObject

A recent change fixed the texture format parameter to be RGB instead
of RGBA for opaque internal formats. However, this broke the RGB10
case, since the pixel type is then GL_UNSIGNED_INT_2_10_10_10_REV. The
doc says:

"GL_INVALID_OPERATION is generated if type is [...]
GL_UNSIGNED_INT_2_10_10_10_REV [...] and format is neither GL_RGBA nor
GL_BGRA."
https://registry.khronos.org/OpenGL-Refpages/gl4/html/glTexImage2D.xhtml

This modifies ba9e57d65f.

Pick-to: 6.7 6.6 6.5
Change-Id: I9a004331513179a3f840a007af0418d14e7f5dff
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

src/opengl/qopenglframebufferobject.cpp

@@ -553,12 +553,14 @@ void QOpenGLFramebufferObjectPrivate::initTexture(int idx)
     bool isOpaque = false;
     switch (color.internalFormat) {
     case GL_RGB8:
-    case GL_RGB10:
     case GL_RGB16:
     case GL_RGB16F:
     case GL_RGB32F:
         isOpaque = true;
         break;
+    case GL_RGB10:
+        // opaque but the pixel type (INT_2_10_10_10) has alpha and so requires RGBA texture format
+        break;
     }
     const GLuint textureFormat = isOpaque ? GL_RGB : GL_RGBA;