arch/x86: (Intel64) use per-CPU parameter struct for CPU startup

A new 'struct x86_cpuboot' is created as well as an instance called
'x86_cpuboot[]' which contains per-CPU boot data (initial stack,
entry function/arg, selectors, etc.). The locore now consults this
table to set up per-CPU registers, etc. during early boot.

Also, rename tss.c to cpu.c as its scope is growing.

Signed-off-by: Charles E. Youse <charles.youse@intel.com>

arch/x86/core/intel64/cpu.c

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2019 Intel Corporation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <kernel.h>
+#include <kernel_arch_data.h>
+#include <kernel_arch_func.h>
+#include <kernel_structs.h>
+#include <arch/x86/multiboot.h>
+
+extern FUNC_NORETURN void z_x86_prep_c(struct multiboot_info *);
+
+extern u8_t _exception_stack[];
+
+Z_GENERIC_SECTION(.tss)
+struct x86_tss64 tss0 = {
+	.ist1 = (u64_t) _interrupt_stack + CONFIG_ISR_STACK_SIZE,
+	.ist7 = (u64_t) _exception_stack + CONFIG_EXCEPTION_STACK_SIZE,
+	.iomapb = 0xFFFF,	/* no I/O access bitmap */
+	.cpu = &(_kernel.cpus[0])
+};
+
+struct x86_cpuboot x86_cpuboot[] = {
+	{
+		.tr = X86_KERNEL_CPU0_TR,
+		.gs = X86_KERNEL_CPU0_GS,
+		.sp = (u64_t) _interrupt_stack + CONFIG_ISR_STACK_SIZE,
+		.fn = z_x86_prep_c
+	}
+};