tracing/histogram: Optimize division by constants

If the divisor is a constant use specific division functions to
avoid extra branches when the trigger is hit.

If the divisor constant but not a power of 2, the division can be
replaced with a multiplication and shift in the following case:

Let X = dividend and Y = divisor.

Choose Z = some power of 2. If Y <= Z, then:
    X / Y = (X * (Z / Y)) / Z

(Z / Y) is a constant (mult) which is calculated at parse time, so:
    X / Y = (X * mult) / Z

The division by Z can be replaced by a shift since Z is a power of 2:
    X / Y = (X * mult) >> shift

As long, as X < Z the results will not be off by more than 1.

Link: https://lkml.kernel.org/r/[email protected]

Suggested-by: Steven Rostedt <[email protected]>
Signed-off-by: Kalesh Singh <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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