ARM: 9051/1: vdso: remove unneded extra-y addition

The vdso linker script is prepocessed on demand. Adding it to 'targets'
is enough, and line 13 of this Makefile does that. This extra-y addition
is unneeded.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>