cpu/x86/sipi: Add x86_64 support

Enter long mode on secondary APs.

Tested on Lenovo T410 with additional x86_64 patches.
Tested on HP Z220 with additional x86_64 patches.

Still boots on x86_32.

Change-Id: I916dd8482d56c7509af9ad0d3b9c28bdc48fd0b1
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37395
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/cpu/x86/sipi_vector.S

@@ -192,11 +192,24 @@ load_msr:
 	mov	%eax, %cr4
 #endif
 
+#ifdef __x86_64__
+	/* entry64.inc preserves ebx. */
+#include <cpu/x86/64bit/entry64.inc>
+
+	mov	%rsi, %rdi	/* cpu_num */
+
+	movl	c_handler, %eax
+	call	*%rax
+#else
 	/* c_handler(cpu_num), preserve proper stack alignment */
 	sub	$12, %esp
 	push	%esi	/* cpu_num */
+
 	mov	c_handler, %eax
 	call	*%eax
+#endif
+
+
 halt_jump:
 	hlt
 	jmp	halt_jump