amd-gpu-x11-mx51: use x11 compatible eglplatform.h
Freescale's default eglplatform.h contains framebuffer headers while
X11 compatible headers are located in eglplatform_1.4.h [1], therefore
overwrite eglplatform.h with eglplatform_1.4.h during install.
This fixes EGL on X support through xcb.
For instance Qt5 would fail to enable CFG_EGL_X [2] due to the
following build error during configure :
invalid conversion from 'EGLNativeDisplayType {aka void*}' to
'Display* {aka _XDisplay*}' [-fpermissive]
This further resulted in a runtime error with Qt5_CinematicExperience:
QXcbIntegration: Cannot create platform OpenGL context, neither GLX
nor EGL are enabled
