Bail early if trying to erase protected sector and also do not double-erase already
erased sectors.
Change-Id: Ic2d39af48c3b8e10e78d52dd978b9bc01f671c6a
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-on: http://openocd.zylin.com/2026
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>