arm: Handle .gnu.hash section in ldscripts

Avoids "could not find output section .gnu.hash" ld.bfd errors on openSUSE.

Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>