ARM: 8375/1: disable some options on ARMv7-M

Kprobes, irqflags tracing and kexec don't currently build on
kernels targetting ARMv7-M, so for now, we should just disallow
those combinations.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>