drivers/cpu: Add generic armv8 cpu driver

Add a generic driver that binds to armv8 CPU nodes. The generic driver allows
- to enumerate CPUs present in a system, even when no other driver binds it
- generates ACPI SSDT code for each CPU
- Fill the ACPI MADT table (implemented in a follow up patch)

The newly introduced code could also be reused on other CPU drivers that are
compatible with armv8.

TEST: Booted on QEMU sbsa and verify the driver binds to CPU nodes.
      Confirmed with FWTS that all ACPI processor devices are present.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Cc: Simon Glass <sjg@chromium.org>
diff --git a/drivers/cpu/Makefile b/drivers/cpu/Makefile
index bc75d9b..7733956 100644
--- a/drivers/cpu/Makefile
+++ b/drivers/cpu/Makefile
@@ -6,10 +6,12 @@
 
 obj-$(CONFIG_CPU) += cpu-uclass.o
 
+
 obj-$(CONFIG_ARCH_BMIPS) += bmips_cpu.o
 obj-$(CONFIG_ARCH_IMX8) += imx8_cpu.o
 obj-$(CONFIG_ARCH_AT91) += at91_cpu.o
 obj-$(CONFIG_ARCH_MEDIATEK) += mtk_cpu.o
+obj-$(CONFIG_CPU_ARMV8) += armv8_cpu.o
 obj-$(CONFIG_CPU_IMX) += imx8_cpu.o
 obj-$(CONFIG_CPU_MPC83XX) += mpc83xx_cpu.o
 obj-$(CONFIG_CPU_RISCV) += riscv_cpu.o