'v' could be an Ice::Variable or Ice::Constant, both of which derive
from Ice::Operand. This was just a slip, the function was always meant
to cast to the return type, Ice::Operand*.

Bug: chromium:1047150
Change-Id: I88414de1c56504eafae17c483c7bb574b269a587
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/40728
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>