[RISCV] Merge more rv32/rv64 intrtinsic tests that have (or should have) the same content. NFC

We weren't testing i64 vrgather.vv on rv32.

Author: topperc

llvm/test/CodeGen/RISCV/rvv/mask-exts-truncs-rv64.ll

@@ -1,5 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=riscv32 -mattr=+v -verify-machineinstrs < %s | FileCheck %s
+; RUN: sed 's/iXLen/i32/g' %s | llc -mtriple=riscv32 -mattr=+v \
+; RUN:   -verify-machineinstrs  | FileCheck %s
+; RUN: sed 's/iXLen/i64/g' %s | llc -mtriple=riscv64 -mattr=+v \
+; RUN:   -verify-machineinstrs  | FileCheck %s
 
 define <vscale x 1 x i8> @sext_nxv1i1_nxv1i8(<vscale x 1 x i1> %v) {
 ; CHECK-LABEL: sext_nxv1i1_nxv1i8: