libpayload: Add x86_64 (64-bit) support

This patch introduces x86_64 (64-bit) support to the payload, building
upon the existing x86 (32-bit) architecture. Files necessary for 64-bit
compilation are now guarded by the `CONFIG_LP_ARCH_X86_64` Kconfig
option.

BUG=b:242829490
TEST=Entered libpayload in long mode, successfully parsed coreboot
table.

Change-Id: I69fda47bedf1a14807b1515c4aed6e3a1d5b8585
Signed-off-by: Subrata Banik <subratabanik@google.com>
---
M payloads/libpayload/Kconfig
M payloads/libpayload/Makefile
M payloads/libpayload/Makefile.mk
A payloads/libpayload/arch/x64/Kconfig
A payloads/libpayload/arch/x64/Makefile.mk
A payloads/libpayload/arch/x64/apic.c
A payloads/libpayload/arch/x64/boot_media.c
A payloads/libpayload/arch/x64/cache.c
A payloads/libpayload/arch/x64/coreboot.c
A payloads/libpayload/arch/x64/delay.c
A payloads/libpayload/arch/x64/exception.c
A payloads/libpayload/arch/x64/exception_asm.S
A payloads/libpayload/arch/x64/exec.S
A payloads/libpayload/arch/x64/gdb.c
A payloads/libpayload/arch/x64/head.S
A payloads/libpayload/arch/x64/libpayload.ldscript
A payloads/libpayload/arch/x64/main.c
A payloads/libpayload/arch/x64/multiboot.c
A payloads/libpayload/arch/x64/selfboot.c
A payloads/libpayload/arch/x64/string.c
A payloads/libpayload/arch/x64/sysinfo.c
A payloads/libpayload/arch/x64/timer.c
A payloads/libpayload/arch/x64/util.S
A payloads/libpayload/arch/x64/virtual.c
M payloads/libpayload/arch/x86/exception.c
A payloads/libpayload/arch/x86/exception_asm_64.S
A payloads/libpayload/arch/x86/exec_64.S
M payloads/libpayload/arch/x86/gdb.c
A payloads/libpayload/arch/x86/head_32.S
A payloads/libpayload/arch/x86/head_64.S
M payloads/libpayload/arch/x86/main.c
M payloads/libpayload/arch/x86/multiboot.c
M payloads/libpayload/arch/x86/string.c
M payloads/libpayload/bin/lpgcc
M payloads/libpayload/drivers/storage/ahci_common.c
M payloads/libpayload/drivers/usb/uhci.c
M payloads/libpayload/drivers/usb/xhci.c
M payloads/libpayload/include/sysinfo.h
A payloads/libpayload/include/x64/arch/apic.h
A payloads/libpayload/include/x64/arch/barrier.h
A payloads/libpayload/include/x64/arch/cache.h
A payloads/libpayload/include/x64/arch/cpuid.h
A payloads/libpayload/include/x64/arch/exception.h
A payloads/libpayload/include/x64/arch/io.h
A payloads/libpayload/include/x64/arch/msr.h
A payloads/libpayload/include/x64/arch/rdtsc.h
A payloads/libpayload/include/x64/arch/types.h
A payloads/libpayload/include/x64/arch/virtual.h
M payloads/libpayload/libc/time.c
M payloads/libpayload/sample/Makefile
M payloads/libpayload/vboot/Makefile.mk
51 files changed, 3,849 insertions(+), 10 deletions(-)