tcl: am437x: disable watchdog on reset-end

tcl: am437x: disable watchdog on reset-end

sometimes, watchdog might be left running and
it could expire in the middle of a debug session,
to prevent that, just make sure to disable watchdog
on reset-end if current state is 'halted'.

Change-Id: Ib4f2a2321cba17cd8c56ca3ae63114a563a6de90
Tested-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Reviewed-on: http://openocd.zylin.com/2615
Tested-by: jenkins
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>