accel/Kconfig: Extract accel selectors into their own config

Move the accel selectors from the global Kconfig.host to their
own Kconfig file.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/accel/Kconfig b/accel/Kconfig
new file mode 100644
index 0000000..c21802b
--- /dev/null
+++ b/accel/Kconfig
@@ -0,0 +1,6 @@
+config KVM
+    bool
+
+config XEN
+    bool
+    select FSDEV_9P if VIRTFS