ArmPkg/ArmLib: don't invalidate entire I-cache on range operation

ArmPkg/ArmLib: don't invalidate entire I-cache on range operation

Instead of cleaning the data cache to the PoU by virtual address and
subsequently invalidating the entire I-cache, invalidate only the
range that we just cleaned. This way, we don't invalidate other
cachelines unnecessarily.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>