[SVE] Fix SVEDup0 matching -0.0f

Because of D128669, CPY is being used to zero active lanes even in the case of -0.0f. This patch checks for floating point positive zero. That way SVEDup0 won't match -0.0f.

Fixes https://github.com/llvm/llvm-project/issues/57428

Reviewed By: paulwalker-arm

Differential Revision: https://reviews.llvm.org/D132880