sparc: remove obsolete ELF support in piggyback_32.c

As we always convert to a.out there is no need to
support ELF.

Removing ELF support because:
- it is not used
- it simplifies code to support a.out only

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>