tcl/target: Enable using vectreset for CC3320SF targets

On CC32xx family of devices, sysrequest is disabled, and
vectreset is blocked by the boot loader (stops in a while(1)
statement). srst reset can leave the target in a state
that prevents debug.

This change enables using vectreset on SF variants by
moving the PC to the start of the user application in
internal flash. This allows for a more reliable reset,
but with two caveats:

1) This only works for the SF variant with internal
   flash.

2) This only resets the CPU and not any peripherals.

Tested on CC3220SF rev B Launchpad in both SWD and
JTAG modes. Confirmed proper behavior of reset,
reset init, reset halt, and reset run commands.

Update: reworked per comment in code review. Re-tested
with CC3220SF Launchpad as both CC3220SF and as
CC32xx board to confirm reset behavior as expected.

Update: Added adapter srst delay 1100 line to the
CC3200 LaunchXL configuration file.

Change-Id: Ibc042d785c846c2223ae55b8f2410b75ed2df354
Signed-off-by: Edward Fewell <efewell@ti.com>
Reviewed-on: http://openocd.zylin.com/5489
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

tcl/target/ti_cc32xx.cfg

@@ -59,6 +59,3 @@ if { [info exists WORKAREASIZE] } {
 }
 
 $_TARGETNAME configure -work-area-phys 0x20000000 -work-area-size $_WORKAREASIZE -work-area-backup 0
-
-reset_config srst_only
-adapter srst delay 1100