[PATCH 3/3] elf: Extract glibcelf constants from <elf.h>

[Florian Weimer]

* Florian Weimer via Libc-alpha:

> +_register_elf_h(DtALTERA_NIOS2, prefix='DT_ALTERA_NIOS2_',
> +                skip=_dt_skip, parent=Dt)

The prefix is non-regular here, it should be 'DT_NIOS_2_'.  Fixed
locally.

Thanks,
Florian