boards/arm: Remove 1000 Hz tick rate on STM32 boards

These all have what appears to be a promiscuously cut-and-pasted
declaration for a 1000 Hz tick rate.  They are all SysTick boards and
will work very well with the new 10 kHz default, so use that instead.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>