kconfig: introduce kconfig files

The Kconfig files were generated mostly with this script:

  for i in `grep -ho CONFIG_[A-Z0-9_]* default-configs/* | sort -u`; do
    set fnord `git grep -lw $i -- 'hw/*/Makefile.objs' `
    shift
    if test $# = 1; then
      cat >> $(dirname $1)/Kconfig << EOF
config ${i#CONFIG_}
    bool

EOF
      git add $(dirname $1)/Kconfig
    else
      echo $i $*
    fi
  done
  sed -i '$d' hw/*/Kconfig
  for i in hw/*; do
    if test -d $i && ! test -f $i/Kconfig; then
      touch $i/Kconfig
      git add $i/Kconfig
    fi
  done

Whenever a symbol is referenced from multiple subdirectories, the
script prints the list of directories that reference the symbol.
These symbols have to be added manually to the Kconfig files.

Kconfig.host and hw/Kconfig were created manually.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20190123065618.3520-27-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/usb/Kconfig

@@ -0,0 +1,53 @@
+config USB
+    bool
+
+config USB_UHCI
+    bool
+
+config USB_OHCI
+    bool
+
+config USB_EHCI
+    bool
+
+config USB_EHCI_SYSBUS
+    bool
+
+config USB_XHCI
+    bool
+
+config USB_XHCI_NEC
+    bool
+
+config USB_MUSB
+    bool
+
+config TUSB6010
+    bool
+
+config USB_TABLET_WACOM
+    bool
+
+config USB_STORAGE_BOT
+    bool
+
+config USB_STORAGE_UAS
+    bool
+
+config USB_AUDIO
+    bool
+
+config USB_SERIAL
+    bool
+
+config USB_NETWORK
+    bool
+
+config USB_BLUETOOTH
+    bool
+
+config USB_SMARTCARD
+    bool
+
+config USB_STORAGE_MTP
+    bool