alpha: mark jensen as broken

CONFIG_ALPHA_JENSEN has failed to compile since commit 6aca0503
("alpha/dma: use common noop dma ops"), so mark it as broken.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

arch/alpha/Kconfig

@@ -209,6 +209,7 @@ config ALPHA_EIGER
 
 config ALPHA_JENSEN
 	bool "Jensen"
+	depends on BROKEN
 	help
 	  DEC PC 150 AXP (aka Jensen): This is a very old Digital system - one
 	  of the first-generation Alpha systems. A number of these systems