[AIE2PS] Fixup L spill test to not use CSR register for return

The test was using CSR registers for function returns which led to the
reload happening before the PseudoRET where it would have to be
afterwards for a normal use. We ended up returning the l register that
was saved from the caller function instead of the one defined inside the
function.
This fixes the test to show realistic MIR where the register is used by
a KILL instruction instead of the PseudoRET, now the reload happens
after the KILL and right before the return restoring the CSR value
coming from the caller.

Author: khallouh

llvm/test/CodeGen/AIE/aie2ps/spill/spill-reload-l.mir

@@ -36,15 +36,17 @@ body:             |
     ; CHECK-NEXT: ST_dms_sts_scalar_spill killed $r3, -48, implicit $sp :: (store (s32) into %stack.0)
     ; CHECK-NEXT: renamable $l7 = COPY $l0
     ; CHECK-NEXT: PseudoJL 32, csr_aie2ps, implicit-def $lr
-    ; CHECK-NEXT: $r1 = LDA_dms_lda_scalar_spill -48, implicit $sp :: (load (s32) from %stack.0)
+    ; CHECK-NEXT: renamable $l0 = KILL killed renamable $l7, implicit $l4, implicit $r11, implicit $l5, implicit $l6
+    ; CHECK-NEXT: $r3 = LDA_dms_lda_scalar_spill -48, implicit $sp :: (load (s32) from %stack.0)
     ; CHECK-NEXT: $l7 = LDA_dml_lda_scalar_L_spill -56, implicit $sp :: (load (s64) from %stack.2)
     ; CHECK-NEXT: $lr = LDA_dms_lda_scalar_spill -44, implicit $sp :: (load (s32) from %stack.1)
     ; CHECK-NEXT: frame-destroy PADDXM_pstm_sp_imm -64, implicit-def $sp, implicit $sp
-    ; CHECK-NEXT: PseudoRET implicit $lr, implicit killed renamable $r1, implicit killed renamable $l7, implicit $l4, implicit $r11, implicit $l5, implicit $l6
+    ; CHECK-NEXT: PseudoRET implicit $lr, implicit killed renamable $r3, implicit killed renamable $l0
     %0:er = LDA_dms_lda_scalar_spill %fixed-stack.0, implicit $sp
     %1:el = COPY $l0
     PseudoJL 32, csr_aie2ps, implicit-def $lr
-    PseudoRET implicit $lr, implicit %0, implicit %1, implicit $l4, implicit $r11, implicit $l5, implicit $l6
+    %2:el = KILL %1, implicit $l4, implicit $r11, implicit $l5, implicit $l6
+    PseudoRET implicit $lr, implicit %0, implicit %2
 ...