ARM: Kconfig: remove useless "default n"

The default for Kconfig options is always n, so there's no need to
explicitly state a "n" default.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>