Update to version 1.9.0

Bump version information for 1.9.0 release
Signed-off-by: David Brown <david.brown@linaro.org>

README.md

@@ -16,7 +16,7 @@
 [travis]: https://travis-ci.org/mcu-tools/mcuboot
 [license]: https://github.com/mcu-tools/mcuboot/blob/main/LICENSE
 
-This is MCUboot version 1.9.0-rc2
+This is MCUboot version 1.9.0
 
 MCUboot is a secure bootloader for 32-bits microcontrollers. It defines a
 common infrastructure for the bootloader and the system flash layout on

docs/release-notes.md

@@ -31,6 +31,7 @@ been tested with a `BOOT_MAX_ALIGN` up to 32 bytes.
 - Remove zephyr example test running in shell.  The Go version is
   primary and much more featureful.
 - imgtool: make `--max-align` default reasonable in most cases.
+- Implement the mcumgr echo command in serial boot mode
 
 ### Security fixes
 

scripts/imgtool/__init__.py

@@ -14,4 +14,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-imgtool_version = "1.9.0rc2"
+imgtool_version = "1.9.0"