smp: move command deprecation to startup.tcl

smp: move command deprecation to startup.tcl

Commit 246782229f8f ("smp: replace commands smp_on/smp_off with
"smp [on|off]"") deprecates some multi-word comments, when openocd
was unable to properly handle mixes of multi-word commands and tcl
procedures having a common initial word.
This limitation is over, so move in startup.tcl the multi-word
commands deprecation, making it easy to remove them after a grace
period.

Change-Id: Icb550d1fa7559b95692d2a1244880da6c90ec0b2
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5677
Tested-by: jenkins