ARM: 7120/1: remove bashism in check for multiple zreladdrs

Get rid of this complaint from dash:

    AS      arch/arm/boot/compressed/lib1funcs.o
  /bin/sh: 1: [: y: unexpected operator
    LD      arch/arm/boot/compressed/vmlinux

Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>