egl: if texture_pixmap_x11_create fails free priv data
egl: if texture_pixmap_x11_create fails free priv data

This makes sure the egl winsys frees the private egl_tex_pixmap state if
in _cogl_winsys_texture_pixmap_x11_create if there is a failure to
create an EGLImage.

Reviewed-by: Neil Roberts <822ec91a7ef82248fd36162ca8ac3283eba70848@linux.intel.com>

djdeath/cogl-android,gcampax/cogl,spatulasnout/cogl,djdeath/cogl,Distrotech/cogl,collects/cogl,Distrotech/cogl,gcampax/cogl,Distrotech/cogl,djdeath/cogl-android,Distrotech/cogl,spatulasnout/cogl,gcampax/cogl,gcampax/cogl,collects/cogl,djdeath/cogl,djdeath/cogl,djdeath/cogl-android