irq: GENERIC_IRQ_MULTI_HANDLER conflicts with MULTI_IRQ_HANDLER

These define the same symbol so they're mutually exclusive.  By the end
of this patch set I'll have removed MULTI_IRQ_HANDLER, but for now it's
slightly easier to make these as conflicting so architectures that now
define MULTI_IRQ_HANDLER won't get the generic version selected by
randconfig.

This will go away when every port is converted over to
GENERIC_IRQ_MULTI_HANDLER.
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

kernel/irq/Kconfig

@@ -134,6 +134,7 @@ config GENERIC_IRQ_DEBUGFS
 endmenu
 
 config GENERIC_IRQ_MULTI_HANDLER
+	depends on !MULTI_IRQ_HANDLER
 	bool
 	help
 	  Allow to specify the low level IRQ handler at run time.