powerpc/udbg: Fix Kconfig entry for avoiding 44x early debug with KVM

It was preventing the global early debug selection whenever KVM was enabled
instead of only preventing the 440 specific one.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Kconfig.debug

@@ -141,9 +141,6 @@ config BOOTX_TEXT
 
 config PPC_EARLY_DEBUG
 	bool "Early debugging (dangerous)"
-	# PPC_EARLY_DEBUG on 440 leaves AS=1 mappings above the TLB high water
-	# mark, which doesn't work with current 440 KVM.
-	depends on !KVM
 	help
 	  Say Y to enable some early debugging facilities that may be available
 	  for your processor/board combination. Those facilities are hacks
@@ -222,7 +219,9 @@ config PPC_EARLY_DEBUG_BEAT
 
 config PPC_EARLY_DEBUG_44x
 	bool "Early serial debugging for IBM/AMCC 44x CPUs"
-	depends on 44x
+	# PPC_EARLY_DEBUG on 440 leaves AS=1 mappings above the TLB high water
+	# mark, which doesn't work with current 440 KVM.
+	depends on 44x && !KVM
 	help
 	  Select this to enable early debugging for IBM 44x chips via the
 	  inbuilt serial port.  If you enable this, ensure you set