Add support for per-processor bug checking - each processor function
descriptor gains a function pointer for this check, which must not be
an __init function.  If non-NULL, this will be called whenever a CPU
enters the kernel via which ever path (boot CPU, secondary CPU startup,
CPU resuming, etc.)

This allows processor specific bug checks to validate that workaround
bits are properly enabled by firmware via all entry paths to the kernel.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Boot-tested-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>