x86/boot/64: Rename start_cpu()

It doesn't really start a CPU but does a far jump to C code. So call it
that. Eliminate the unconditional JMP to it from secondary_startup_64()
but make the jump to C code piece part of secondary_startup_64()
instead.

Also, it doesn't need to be a global symbol either so make it a local
label. One less needlessly global symbol in the symbol table.

No functionality change.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170304095611.11355-1-bp@alien8.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/head_64.S

@@ -269,10 +269,8 @@ ENTRY(secondary_startup_64)
 	/* rsi is pointer to real mode structure with interesting info.
 	   pass it to C */
 	movq	%rsi, %rdi
-	jmp	start_cpu
-ENDPROC(secondary_startup_64)
 
-ENTRY(start_cpu)
+.Ljump_to_C_code:
 	/*
 	 * Jump to run C code and to be on a real kernel address.
 	 * Since we are running on identity-mapped space we have to jump
@@ -305,7 +303,7 @@ ENTRY(start_cpu)
 	pushq	%rax		# target address in negative space
 	lretq
 .Lafter_lret:
-ENDPROC(start_cpu)
+ENDPROC(secondary_startup_64)
 
 #include "verify_cpu.S"
 
@@ -313,11 +311,11 @@ ENDPROC(start_cpu)
 /*
  * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
  * up already except stack. We just set up stack here. Then call
- * start_secondary() via start_cpu().
+ * start_secondary() via .Ljump_to_C_code.
  */
 ENTRY(start_cpu0)
 	movq	initial_stack(%rip), %rsp
-	jmp	start_cpu
+	jmp	.Ljump_to_C_code
 ENDPROC(start_cpu0)
 #endif