Fixed RGBA <-> BGRA bug in EGLFS backingstore.

Better to swizzle in the fragment shader than to do a byte swapping
operation on the CPU.

Change-Id: I01420c3a5ceb5309f5648e1f86979b025bdd88aa
Reviewed-by: Donald Carr <donald.carr@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>

src/plugins/platforms/eglfs/qeglfsbackingstore.cpp

@@ -100,7 +100,7 @@ void QEglFSBackingStore::flush(QWindow *window, const QRegion &region, const QPo
             "uniform sampler2D texture;\n"
             "varying highp vec2 textureCoord;\n"
             "void main() {\n"
-            "   gl_FragColor = texture2D(texture, textureCoord);\n"
+            "   gl_FragColor = texture2D(texture, textureCoord).bgra;\n"
             "}\n";
 
         m_program = new QOpenGLShaderProgram;