x86_64: simplify the memtest parameter setting

use CONFIG_MEMTEST only. if it is set, will have memtest=0 (disabled)

need to have memtest=4 in command line to test more patterns.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 32ba13b..c6d8131 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -431,7 +431,7 @@
 		direct_gbpages = 0;
 }
 
-#ifdef CONFIG_MEMTEST_BOOTPARAM
+#ifdef CONFIG_MEMTEST
 
 static void __init memtest(unsigned long start_phys, unsigned long size,
 				 unsigned pattern)
@@ -493,7 +493,8 @@
 
 }
 
-static int memtest_pattern __initdata = CONFIG_MEMTEST_BOOTPARAM_VALUE;
+/* default is disabled */
+static int memtest_pattern __initdata;
 
 static int __init parse_memtest(char *arg)
 {