zynq_7000.cfg: Fix issue 'Error: can't read "zynq_pl": no such variable'

Change-Id: Ic79ce114b60d0707a6e082a81743b378b164b4e2
Signed-off-by: Dominik Wernberger <dominik.wernberger@gmx.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/8190
Reviewed-by: Daniel Anselmi <danselmi@gmx.ch>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Tested-by: jenkins

tcl/target/zynq_7000.cfg

@@ -47,7 +47,7 @@ ${_TARGETNAME}0 configure -event reset-assert-post "cortex_a dbginit"
 ${_TARGETNAME}1 configure -event reset-assert-post "cortex_a dbginit"
 
 pld create zynq_pl.pld virtex2 -chain-position zynq_pl.bs -no_jstart
-virtex2 set_user_codes $zynq_pl.pld 0x02 0x03 0x22 0x23
+virtex2 set_user_codes zynq_pl.pld 0x02 0x03 0x22 0x23
 
 set XC7_JSHUTDOWN 0x0d
 set XC7_JPROGRAM 0x0b