audit: Add option to enable/disable syscall audit

Enable syscall audit has performance impact on Android, add option to
enable/disable the syscall audits.

Change-Id: I654e553daca388c03774886bf13410e2fdec0b02
Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>
diff --git a/init/Kconfig b/init/Kconfig
index 6a4e13a..007186d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -312,15 +312,20 @@
 	help
 	  Enable auditing infrastructure that can be used with another
 	  kernel subsystem, such as SELinux (which requires this for
-	  logging of avc messages output).  System call auditing is included
-	  on architectures which support it.
+	  logging of avc messages output). Does not do system-call
+	  auditing without CONFIG_AUDITSYSCALL.
 
 config HAVE_ARCH_AUDITSYSCALL
 	bool
 
 config AUDITSYSCALL
-	def_bool y
+	bool "Enable system-call auditing support"
 	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
+	default y if SECURITY_SELINUX
+	help
+	  Enable low-overhead system-call auditing infrastructure that
+	  can be used independently or with another kernel subsystem,
+	  such as SELinux.
 
 config AUDIT_WATCH
 	def_bool y