pmb.config: make qemu-amd64 the default device (!1899)

At the moment we set samsung-i9100 as default device.
This is probably only for historical reasons.

For someone/something using pmbootstrap without a specific device in mind
(e.g. CI) it's really better to use a generic device. QEMU runs natively
in a virtual machine so everyone can use it for testing.

pmb/config/__init__.py

@@ -52,7 +52,7 @@ defaults = {
     # kernel configs
     "cipher": "aes-cbc-plain64",
     "config": os.path.expanduser("~") + "/.config/pmbootstrap.cfg",
-    "device": "samsung-i9100",
+    "device": "qemu-amd64",
     "extra_packages": "none",
     "fork_alpine": False,
     "hostname": "",