[CostModel][AMDGPU] Fix instructions costs estimation for vector types.

1. Fixed vector instructions costs estimations incosistency - removed different
   logic for "not simple types" since it biases costs for these types.
2. Fixed legalization penalty for vectors too big for the target: changed from
   overwrite default legalization cost value estimation to added penalty.
3. Fixed few typos in tests.

Reviewed By: rampitec

Differential Revision: https://reviews.llvm.org/D114893