arch: remove KCORE_ELF again [tile]

The Kconfig symbol KCORE_ELF was removed in v2.6.0, but reappeared in two
architectures. It is useless. Remove it again.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> (tile only)