execute1: Make it clear that divide logic is not included when HAS_FPU=true

execute1: Make it clear that divide logic is not included when HAS_FPU=true

This adds a "not HAS_FPU" condition in a few places to make it obvious
that logic to interface to the divide unit is not included when we
have an FPU.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>