flash/startup.tcl: update stm32 flash driver aliases

flash/startup.tcl: update stm32 flash driver aliases

This will enable us to use either name when calling flash driver commands.

For example the stm32wbx family use the same flash driver as the stm32l4x, so
the user has to use 'stm32l4x lock 0' which can be confusing.
Now the user can also use 'stm32wbx lock 0' with the same result.

Change-Id: Ic0d8da9afc202d7cc82d9b9949827e958a1cc824
Signed-off-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-on: http://openocd.zylin.com/5436
Tested-by: jenkins
Reviewed-by: Marc Schink <dev@zapb.de>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>