ARM: 6533/1: Thumb-2: Make CONFIG_THUMB2_KERNEL depend on !CPU_V6

This makes sense, because Thumb-2 code can't execute on plain
ARMv6 processors.

This will avoid accidentally configuring a broken kernel where the
config otherwise would allow multiple architecture versions to
coexist in the same kernel.

Not adding !CPU_V5 etc., because the chance of anyone trying to
put v5 and v7 in the same kernel is low, and I'm not aware of
any mach which can do this.  These could be added later if it
matters.

Note that the rules may need to be refined if support for the
ARM1156J(F)-S processor is later added to the kernel, since this
processor supports the rare ARMv6T2 extensions, which add support
for Thumb-2 and a few other ARMv7 features.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>