meson.build: enable xenpv machine build for ARM

Add CONFIG_XEN for aarch64 device to support build for ARM targets.

Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

meson.build

@@ -136,7 +136,7 @@ endif
 if cpu in ['x86', 'x86_64', 'arm', 'aarch64']
   # i386 emulator provides xenpv machine type for multiple architectures
   accelerator_targets += {
-    'CONFIG_XEN': ['i386-softmmu', 'x86_64-softmmu'],
+    'CONFIG_XEN': ['i386-softmmu', 'x86_64-softmmu', 'aarch64-softmmu'],
   }
 endif
 if cpu in ['x86', 'x86_64']