cmd/asm/internal/asm: run riscv64 end-to-end tests for each profile

cmd/asm/internal/asm: run riscv64 end-to-end tests for each profile

Currently, the end-to-end tests are only run for the profile set
via GORISCV64. Run each of the end-to-end tests for each profile,
increasing test coverage. Also rename tests to be RISCV64 specific,
rather than RISCV.

Change-Id: I15a70939064122c79ec5f2edcda1fa2a47c8cc95
Reviewed-on: https://go-review.googlesource.com/c/go/+/731921
Auto-Submit: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>