tcl/interface/buspirate: Adapt to new buspirate command syntax

Change-Id: I1a82608532f043054abd22eb5b50ab5c5f58cee4
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: http://openocd.zylin.com/6405
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

tcl/interface/buspirate.cfg

@@ -7,19 +7,19 @@
 adapter driver buspirate
 
 # you need to specify port on which BP lives
-#buspirate_port /dev/ttyUSB0
+#buspirate port /dev/ttyUSB0
 
 # communication speed setting
-buspirate_speed normal ;# or fast
+buspirate speed normal ;# or fast
 
 # voltage regulator Enabled = 1 Disabled = 0
-#buspirate_vreg 0
+#buspirate vreg 0
 
 # pin mode normal or open-drain (jtag only)
-#buspirate_mode normal
+#buspirate mode normal
 
 # pullup state Enabled = 1 Disabled = 0
-#buspirate_pullup 0
+#buspirate pullup 0
 
 # this depends on the cable, you are safe with this option
 reset_config srst_only