x86, generic: mark early_printk as asmlinkage

It's not explicitly marked as asmlinkage, but invoked from x86_32
startup code with parameters on stack.

No other architectures define early_printk and none of them are affected
by this change, since defines asmlinkage as empty token.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/early_printk.c

@@ -196,7 +196,7 @@ static struct console simnow_console = {
 static struct console *early_console = &early_vga_console;
 static int early_console_initialized;
 
-void early_printk(const char *fmt, ...)
+asmlinkage void early_printk(const char *fmt, ...)
 {
 	char buf[512];
 	int n;

include/linux/kernel.h

@@ -207,7 +207,7 @@ static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \
 		{ return false; }
 #endif
 
-extern void __attribute__((format(printf, 1, 2)))
+extern void asmlinkage __attribute__((format(printf, 1, 2)))
 	early_printk(const char *fmt, ...);
 
 unsigned long int_sqrt(unsigned long);

kernel/printk.c

@@ -38,7 +38,7 @@
 /*
  * Architectures can override it:
  */
-void __attribute__((weak)) early_printk(const char *fmt, ...)
+void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
 {
 }