xen: add per-platform defaults for NR_CPUS

Add specific per-platform defaults for NR_CPUS. Note that the order of
the defaults matter: they need to go first, otherwise the generic
defaults will be applied.

This is done so that Xen builds customized for a specific hardware
platform can have the right NR_CPUS number.

Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <julien.grall@arm.com>
CC: JBeulich@suse.com
CC: andrew.cooper3@citrix.com

---

Changes in v6:
- remove useless additional default for ALL

xen/arch/Kconfig

@@ -3,6 +3,9 @@ config NR_CPUS
 	int "Maximum number of physical CPUs"
 	range 1 4095
 	default "256" if X86
+	default "8" if ARM && RCAR3
+	default "4" if ARM && QEMU
+	default "4" if ARM && MPSOC
 	default "128" if ARM
 	---help---
 	  Specifies the maximum number of physical CPUs which Xen will support.