docs/cxl: Replace unsupported AARCH64 with x86_64

Currently Qemu CXL emulation support is not availabe on AARCH64 but its
available with qemu x86_64 architecture, updating the document to reflect
the supported platform.

Signed-off-by: Raghu H <raghuhack78@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20230421134507.26842-4-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

docs/system/devices/cxl.rst

@@ -302,7 +302,7 @@ Example command lines
 ---------------------
 A very simple setup with just one directly attached CXL Type 3 device::
 
-  qemu-system-aarch64 -M virt,gic-version=3,cxl=on -m 4g,maxmem=8G,slots=8 -cpu max \
+  qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
   ...
   -object memory-backend-file,id=cxl-mem1,share=on,mem-path=/tmp/cxltest.raw,size=256M \
   -object memory-backend-file,id=cxl-lsa1,share=on,mem-path=/tmp/lsa.raw,size=256M \
@@ -315,7 +315,7 @@ A setup suitable for 4 way interleave. Only one fixed window provided, to enable
 interleave across 2 CXL host bridges.  Each host bridge has 2 CXL Root Ports, with
 the CXL Type3 device directly attached (no switches).::
 
-  qemu-system-aarch64 -M virt,gic-version=3,cxl=on -m 4g,maxmem=8G,slots=8 -cpu max \
+  qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
   ...
   -object memory-backend-file,id=cxl-mem1,share=on,mem-path=/tmp/cxltest.raw,size=256M \
   -object memory-backend-file,id=cxl-mem2,share=on,mem-path=/tmp/cxltest2.raw,size=256M \
@@ -339,7 +339,7 @@ the CXL Type3 device directly attached (no switches).::
 
 An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
 
-  qemu-system-aarch64 -M virt,gic-version=3,cxl=on -m 4g,maxmem=8G,slots=8 -cpu max \
+  qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
   ...
   -object memory-backend-file,id=cxl-mem0,share=on,mem-path=/tmp/cxltest.raw,size=256M \
   -object memory-backend-file,id=cxl-mem1,share=on,mem-path=/tmp/cxltest1.raw,size=256M \