docs/system/ppc/ppce500: Use qemu-system-ppc64 across the board(s)

The documentation suggests that there is a qemu-system-ppc32 binary
while the 32 bit version is actually just named qemu-system-ppc. Settle
on qemu-system-ppc64 which also works for 32 bit machines and causes
less clutter in the documentation.

Found-by: BALATON Zoltan <balaton@eik.bme.hu>
Suggested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20221018210146.193159-2-shentey@gmail.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

docs/system/ppc/ppce500.rst

@@ -113,7 +113,7 @@ To boot the 32-bit Linux kernel:
 
 .. code-block:: bash
 
-  $ qemu-system-ppc{64|32} -M ppce500 -cpu e500mc -smp 4 -m 2G \
+  $ qemu-system-ppc64 -M ppce500 -cpu e500mc -smp 4 -m 2G \
       -display none -serial stdio \
       -kernel vmlinux \
       -initrd /path/to/rootfs.cpio \
@@ -154,10 +154,10 @@ interface at PCI address 0.1.0, but we can switch that to an e1000 NIC by:
 
 .. code-block:: bash
 
-  $ qemu-system-ppc -M ppce500 -smp 4 -m 2G \
-                    -display none -serial stdio \
-                    -bios u-boot \
-                    -nic tap,ifname=tap0,script=no,downscript=no,model=e1000
+  $ qemu-system-ppc64 -M ppce500 -smp 4 -m 2G \
+                      -display none -serial stdio \
+                      -bios u-boot \
+                      -nic tap,ifname=tap0,script=no,downscript=no,model=e1000
 
 The QEMU ``ppce500`` machine can also dynamically instantiate an eTSEC device
 if “-device eTSEC” is given to QEMU: