Misc. improvements for GPU testing

hercules_ir/src/dot.rs

hercules_ir/src/loops.rs

hercules_opt/src/gcm.rs

hercules_samples/dot/Cargo.toml

hercules_samples/dot/build.rs

hercules_samples/dot/src/cpu.sch

hercules_samples/dot/src/gpu.sch

hercules_samples/matmul/Cargo.toml

hercules_samples/matmul/build.rs

hercules_samples/matmul/src/cpu.sch

hercules_samples/matmul/src/gpu.sch