printk: add dummy routine for when CONFIG_PRINTK=n

There are missing dummy routines for log_buf_addr_get() and
log_buf_len_get() for when CONFIG_PRINTK is not set causing build
failures.

This patch adds these dummy routines at the appropriate location.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/printk.h

@@ -10,9 +10,6 @@
 extern const char linux_banner[];
 extern const char linux_proc_banner[];
 
-extern char *log_buf_addr_get(void);
-extern u32 log_buf_len_get(void);
-
 static inline int printk_get_level(const char *buffer)
 {
 	if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {
@@ -163,6 +160,8 @@ extern int kptr_restrict;
 
 extern void wake_up_klogd(void);
 
+char *log_buf_addr_get(void);
+u32 log_buf_len_get(void);
 void log_buf_kexec_setup(void);
 void __init setup_log_buf(int early);
 void dump_stack_set_arch_desc(const char *fmt, ...);
@@ -198,6 +197,16 @@ static inline void wake_up_klogd(void)
 {
 }
 
+static inline char *log_buf_addr_get(void)
+{
+	return NULL;
+}
+
+static inline u32 log_buf_len_get(void)
+{
+	return 0;
+}
+
 static inline void log_buf_kexec_setup(void)
 {
 }