tcl: [3/3] prepare for jimtcl 0.81 'expr' syntax change

tcl: [3/3] prepare for jimtcl 0.81 'expr' syntax change

Jimtcl commit 1843b79a03dd ("expr: TIP 526, only support a single
arg") drops the support for multi-argument syntax for the TCL
command 'expr'.

Fix manually the remaining lines that don't match simple patterns
and would require dedicated boring scripting.
Remove the 'expr' command where appropriate.

Change-Id: Ia75210c8447f88d38515addab4a836af9103096d
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6161
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>