mm: add missing dependency in Kconfig

Eliminate the following (rand)config warning by adding missing PROC_FS
dependency:

  warning: (HWPOISON_INJECT && MEM_SOFT_DIRTY) selects PROC_PAGE_MONITOR which has unmet direct dependencies (PROC_FS && MMU)

Signed-off-by: Sima Baymani <sima.baymani@gmail.com>
Suggested-by: David Rientjes <rientjes@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/Kconfig

@@ -543,7 +543,7 @@ config ZSWAP
 
 config MEM_SOFT_DIRTY
 	bool "Track memory changes"
-	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY
+	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 	select PROC_PAGE_MONITOR
 	help
 	  This option enables memory changes tracking by introducing a