Update zephyr version files for 2.0.0-rc1

Update for the rc1 release.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/README.md b/README.md
index 5bf3f38..d4a8fb6 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@
 [travis]: https://travis-ci.org/mcu-tools/mcuboot
 [license]: https://github.com/mcu-tools/mcuboot/blob/main/LICENSE
 
-This is MCUboot version 1.11.0-dev
+This is MCUboot version 2.0.0-rc1
 
 MCUboot is a secure bootloader for 32-bits microcontrollers. It defines a
 common infrastructure for the bootloader and the system flash layout on