flash/nor/stm32f1x: Add support for GD32E23x

flash/nor/stm32f1x: Add support for GD32E23x

GD32E23x from GigaDevice is cortex-M23 microcontroller and it can work with the stm32f1x driver.
Modifications are similar to this done for GD32F1x0 in #6164 (https://review.openocd.org/c/openocd/+/6164).
Configuration file is added because its cortex-M23 CPU ID is different.
I think that GigaDevice microcontrollers should be handled in an independent unit to separate them from STM32,
but nowadays quick solution is welcome.

Signed-off-by: asier70Andrzej Sierżęga <asier70@gmail.com>
Change-Id: I91f31f5f66808bc50a8f607ac2c107e6b7c5e2b8
Reviewed-on: https://review.openocd.org/c/openocd/+/6527
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>