Limit dotProduct value to 1.0f, so acosf would not return NaN.

Due to precision loss of float math, we sometimes get 1.000001f for
dotProduct. This causes NaN result from acosf() and floor() funcs.

At the moment, this does not cause any problems on ARM, as casting
NaN to int results in 0. On mips however (possibly on x86), such cast
gives INT_MAX, so crash occurs when trying to use the resulting value.

Change-Id: I8e0285a0306a65b8469d9f4885c19665066fc4c8