egl: propagate EGL_BAD_ATTRIBUTE during EGLImage attr parsing

egl: propagate EGL_BAD_ATTRIBUTE during EGLImage attr parsing

Earlier commit refactored/split the parsing into separate hunks.
While no functional change was intended, it did not attribute that
different error is set when the attrib. value is incorrect.

Fixes:  3ee2be4113d ("egl: split _eglParseImageAttribList into per
extension functions")
Cc: Michel Dänzer <michel@daenzer.net>
Reported-by: Michel Dänzer <michel@daenzer.net>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Tested-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>