target/xscale: change prototype of xscale_verify_pointer()

target/xscale: change prototype of xscale_verify_pointer()

To prepare for handling TCL return values consistently, all calls
to command_print/command_print_sameline should be ready to switch
to CMD as first parameter.

Change prototype of xscale_verify_pointer() to pass CMD instead of
CMD_CTX.

This change was part of http://openocd.zylin.com/1815 from Paul
Fertser and has been extracted and rebased to simplify the review.

Change-Id: Id047fab41ec4f673a46756b0ab901e659e088544
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5064
Tested-by: jenkins