[NRF52] Remove uint64_t div in watchdog init
[NRF52] Remove uint64_t div in watchdog init

Because of precision requirements the watchdog was using a uint64_t
division cause it allowed any possible timeout to be used. This updates the
code to rely only on uint32_t division with the limitation of a maximum
timeout of slightly more than 12 hours. It shrinks the code due to not
linking in the div emulation code.

mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core