arch/x86,cpu/x86: Fix 64-bit CPU_INFO_V2 build errors

There are two possible code sections where the cpu_info macros can be
included: .code32 and .code64

Doing a `push %eax` while in a .code64 section will result in a compiler
error. This macro manually pushes the 32-bit register onto the stack so
we can share the code between 32 and 64 bit builds.

We also can't implicitly dereference per_cpu_segment_selector because
it's a 32-bit address. Trying to do this results in the following:
  E: Invalid reloc type: 11
  E: Illegal use of 32bit sign extended addressing at offset 0x1b2

If we load the address first, then dereference it, we can work around
the limitation.

With these fixes, 64-bit builds can now use CPU_INFO_V2.

BUG=b:179699789
TEST=Boot qemu 64 bit build with CPU_INFO_V2 and 4 CPUs. See AP init
work as expected.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I4e72a808c9583bb2d0f697cbbd9cb9c0aa0ea2dc
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58232
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/arch/x86/c_start.S

@@ -90,7 +90,8 @@ _start:
 	 */
 	set_segment_descriptor_base $per_cpu_segment_descriptors, %esp
 
-	mov	per_cpu_segment_selector, %eax
+	mov	$per_cpu_segment_selector, %eax
+	movl	(%eax), %eax
 	mov	%eax, %gs
 #endif
 

src/cpu/x86/cpu_info.S.inc

@@ -1,14 +1,34 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
+/*
+ * Pushes a 32-bit register onto the stack.
+ *
+ * There are two possible code sections where this code can be included:
+ *   .code32 and .code64
+ *
+ * Doing a `push %eax` while in a .code64 section will result in a compiler
+ * error. This macro manually pushes the 32-bit register onto the stack so we
+ * can share the code between 32 and 64 bit builds.
+ */
+.macro pushr reg:req
+#if ENV_X86_64
+	movl	$0, -4(%esp)
+	movl	\reg, -8(%esp)
+	sub	$8, %esp
+#else
+	push	\reg
+#endif
+.endm
+
 /* Push struct cpu_info */
 .macro push_cpu_info index=$0
-	push	\index	/* index */
-	push	$0	/* *cpu */
+	pushr	\index	/* index (size_t) */
+	pushr	$0	/* *cpu */
 .endm
 
 /* Push struct per_cpu_segment_data */
 .macro push_per_cpu_segment_data cpu_info_pointer=%esp
-	push	\cpu_info_pointer	/* *cpu_info */
+	pushr	\cpu_info_pointer	/* *cpu_info */
 .endm
 
 /*