board: drop open-bldc

This is a) broken and b) doesn't include anything other than the
(broken) target alias.  Don't see any reason for it to exist.

Change-Id: I833635eeac392bf7c0c39f51ff2f76525ba2d406
Signed-off-by: Karl Palsson <karlp@tweak.net.au>
Reviewed-on: http://openocd.zylin.com/5884
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

tcl/board/open-bldc.cfg

@@ -1,7 +0,0 @@
-# Open Source Brush Less DC Motor Controller
-# http://open-bldc.org
-
-# Work-area size (RAM size) = 20kB for STM32F103RB device
-set WORKAREASIZE 0x5000
-
-source [find target/stm32.cfg]