ARM: 5911/1: ARM: Select CPU_32v6K for CPU_V7 only if ARCH_OMAP2 is not selected

Otherwise the kernel built with both CPU_V6 and CPU_V7 will not
boot on omap2.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>