[RISCV][test] Add missing check-prefix to a test (NFC) (#93683)

Author: s-barannikov

llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-abs-rv32.mir

@@ -1,8 +1,8 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 # RUN: llc -mtriple=riscv32 -run-pass=legalizer %s -o - \
-# RUN:   | FileCheck %s --check-prefix=RV32I
+# RUN:   | FileCheck %s --check-prefixes=CHECK,RV32I
 # RUN: llc -mtriple=riscv32 -mattr=+zbb -run-pass=legalizer %s -o -\
-# RUN:   | FileCheck %s --check-prefix=RV32ZBB
+# RUN:   | FileCheck %s --check-prefixes=CHECK,RV32ZBB
 
 ---
 name:            abs_i8
@@ -124,10 +124,12 @@ body:             |
     ; CHECK-NEXT: [[ASHR1:%[0-9]+]]:_(s32) = G_ASHR [[COPY1]], [[C1]](s32)
     ; CHECK-NEXT: [[ADD:%[0-9]+]]:_(s32) = G_ADD [[COPY]], [[ASHR]]
     ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ult), [[ADD]](s32), [[ASHR]]
+    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:_(s32) = COPY [[ADD]](s32)
     ; CHECK-NEXT: [[ADD1:%[0-9]+]]:_(s32) = G_ADD [[COPY1]], [[ASHR1]]
     ; CHECK-NEXT: [[ADD2:%[0-9]+]]:_(s32) = G_ADD [[ADD1]], [[ICMP]]
-    ; CHECK-NEXT: [[XOR:%[0-9]+]]:_(s32) = G_XOR [[ADD]], [[ASHR]]
-    ; CHECK-NEXT: [[XOR1:%[0-9]+]]:_(s32) = G_XOR [[ADD2]], [[ASHR1]]
+    ; CHECK-NEXT: [[COPY3:%[0-9]+]]:_(s32) = COPY [[ADD2]](s32)
+    ; CHECK-NEXT: [[XOR:%[0-9]+]]:_(s32) = G_XOR [[COPY2]], [[ASHR]]
+    ; CHECK-NEXT: [[XOR1:%[0-9]+]]:_(s32) = G_XOR [[COPY3]], [[ASHR1]]
     ; CHECK-NEXT: $x10 = COPY [[XOR]](s32)
     ; CHECK-NEXT: $x11 = COPY [[XOR1]](s32)
     ; CHECK-NEXT: PseudoRET implicit $x10, implicit $x11