target/stm32xx: Endian is not configurable.

target/stm32xx: Endian is not configurable.

So remove it from all the configs, it's misleading, and leads to cargo
culting of config files.

Change-Id: I2b77e60d5e96f9759c7c9fc91b20e73be2e95d9a
Signed-off-by: Karl Palsson <karlp@tweak.net.au>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2446
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>