more tcl/{board,target} cleanup

Remove more remnants of the old "jtag_device" syntax.

Don't [format "%s.cpu" $_CHIPNAME] ... it's needless complexity.

Remove various non-supported "-variant" target options; they're not
needed often at all.

Flag some of the board files as needing to have and use target files
for the TAP and target declarations.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

tcl/board/at91eb40a.cfg

@@ -1,5 +1,9 @@
 #Script for AT91EB40a
 
+# FIXME use some standard target config, maybe create one from this
+#
+#	source [find target/...cfg]
+
 if { [info exists CHIPNAME] } {
    set  _CHIPNAME $CHIPNAME
 } else {
@@ -30,12 +34,11 @@ if { [info exists CPUTAPID ] } {
 reset_config srst_only srst_pulls_trst
 
 #jtag scan chain
-#format L IRC IRCM IDCODE (Length, IR Capture, IR Capture Mask, IDCODE)
 jtag newtap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf -expected-id $_CPUTAPID
 
 #target configuration
 set _TARGETNAME $_CHIPNAME.cpu
-target create $_TARGETNAME arm7tdmi -endian $_ENDIAN -chain-position $_TARGETNAME -variant arm7tdmi-s_r4
+target create $_TARGETNAME arm7tdmi -endian $_ENDIAN -chain-position $_TARGETNAME
 
 # speed up memory downloads
 arm7_9 fast_memory_access enable