x86: sanitize Kconfig

Set default n for MEMTEST and MTRR_SANITIZER and fix the help texts.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/Kconfig

@@ -447,7 +447,6 @@ config PARAVIRT_DEBUG
 config MEMTEST
 	bool "Memtest"
 	depends on X86_64
-	default y
 	help
 	  This option adds a kernel parameter 'memtest', which allows memtest
 	  to be set.
@@ -455,7 +454,7 @@ config MEMTEST
 		memtest=1, mean do 1 test pattern;
 		...
 		memtest=4, mean do 4 test patterns.
-	  If you are unsure how to answer this question, answer Y.
+	  If you are unsure how to answer this question, answer N.
 
 config X86_SUMMIT_NUMA
 	def_bool y
@@ -1135,21 +1134,18 @@ config MTRR
 	  See <file:Documentation/mtrr.txt> for more information.
 
 config MTRR_SANITIZER
-	def_bool y
+	bool
 	prompt "MTRR cleanup support"
 	depends on MTRR
 	help
-	  Convert MTRR layout from continuous to discrete, so some X driver
-	  could add WB entries.
+	  Convert MTRR layout from continuous to discrete, so X drivers can
+	  add writeback entries.
 
-	  Say N here if you see bootup problems (boot crash, boot hang,
-	  spontaneous reboots).
+	  Can be disabled with disable_mtrr_cleanup on the kernel command line.
+	  The largest mtrr entry size for a continous block can be set with
+	  mtrr_chunk_size.
 
-	  Could be disabled with disable_mtrr_cleanup. Also mtrr_chunk_size
-	  could be used to send largest mtrr entry size for continuous block
-	  to hold holes (aka. UC entries)
-
-	  If unsure, say Y.
+	  If unsure, say N.
 
 config MTRR_SANITIZER_ENABLE_DEFAULT
 	int "MTRR cleanup enable value (0-1)"
@@ -1166,7 +1162,7 @@ config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
 	depends on MTRR_SANITIZER
 	help
 	  mtrr cleanup spare entries default, it can be changed via
-	  mtrr_spare_reg_nr=
+	  mtrr_spare_reg_nr=N on the kernel command line.
 
 config X86_PAT
 	bool