EGL 1.5 cleanup eglGetPlatformDisplay

Generation scripts cannot create code for eglGetPlatformDisplay,
(prior CL modified code by hand after generation)
this change removes the need for generating code for that function.
Also include eglCreateImage and eglDestroyImage in EGL15.spec file.

Bug: 80297325
Test: atest CtsGraphicsTestCases:EGL15Test
Change-Id: I18e2f8fe43a43e6f74f4687af28c656dd9f65bc0