use correct -march for x86_64

target/config/Config.in.cpu

@@ -108,7 +108,7 @@ config ADK_TARGET_CPU_ARCH
 	string
 	default "x86_64" if ADK_CPU_X86_64
 	default "x86_64" if ADK_CPU_AMDFAM10
-	default "x86_64" if ADK_CPU_ATHLON
+	default "i686" if ADK_CPU_ATHLON
 	default "i486" if ADK_CPU_I486
 	default "i586" if ADK_CPU_I586
 	default "i686" if ADK_CPU_I686

target/config/Config.in.target

@@ -12,7 +12,7 @@ config ADK_TARGET_CFLAGS
 	default "-march=i486" if ADK_CPU_I486
 	default "-march=i586" if ADK_CPU_I586
 	default "-march=i686" if ADK_CPU_I686
-	default "-mtune=generic" if ADK_CPU_X86_64
+	default "-march=x86-64" if ADK_CPU_X86_64
 	default "-march=athlon" if ADK_CPU_ATHLON
 	default "-march=pentium-m" if ADK_CPU_PENTIUM_M
 	default "-march=atom" if ADK_CPU_ATOM

target/x86_64/systems/qemu-x86_64

@@ -2,7 +2,7 @@ config ADK_TARGET_SYSTEM_QEMU_X86_64
 	bool "Qemu Emulator"
 	select ADK_x86_64
 	select ADK_qemu_x86_64
-	select ADK_CPU_ATHLON
+	select ADK_CPU_X86_64
 	select ADK_LINUX_64
 	select ADK_TARGET_QEMU
 	select ADK_TARGET_KERNEL_BZIMAGE