Force the SysTick clock bit to be set in Cortex-M3 and Cortex-M4F bits if configSYSTI...

Force the SysTick clock bit to be set in Cortex-M3 and Cortex-M4F bits if configSYSTICK_CLOCK_HZ is not defined, otherwise leave the bit as it is found as the SysTick may use a divided clock.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2134 1d2547de-c912-0410-9cb9-b8ca96c0e9e2