The previous computation incorrectly assumed that the uint32_t ticks
counter MICROPY_SOFT_TIMER_TICKS_MS was in the range [0,0x80000000) where
its actually [0,0xffffffff]. This means the diff calculation can be
simplified compared to the original implementation copied from
utime_mphal.c, which has to deal with a ticks range constrained by the
small int range.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
b1cdb205ec