soc/arm: Remove 1 kHz tick rate default for mcimx7_m4 and msp432p401r

As with the STM32 boards, these had an existing default for tick rate
that is now lower than the 10 kHz default.  They're SysTick devices
that can handle the higher rate just fine.  Use that.

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