stm32: determine all cpu types and use common examine

stm32: determine all cpu types and use common examine

This patch determine all cpu types and not only
the cortex M3 and the stm32 target use the common
target examine function from the cortex_m sources.

Change-Id: If689dd994b3855284b927fc4b206f420cf32b6c7
Signed-off-by: Mathias K <kesmtp@freenet.de>
Reviewed-on: http://openocd.zylin.com/511
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>