[PowerPC] Fix td pattern for P10 VSLDBI and VSRDBI

[quinnp]

Summary

This patch fixes the pattern for the P10 instructions Vector Shift Left
Double by Bit Immediate VN-form and Vector Shift Right Double by Bit
Immediate VN-form. The third argument should be a target constant (timm)
instead of an i32 because an immediate is expected.

[lei]

LGTM
Thx!

llvm/lib/Target/PowerPC/PPCInstrPrefix.td

let Predicates = [IsISA3_1] in {
 
   def VSLDBI : VNForm_VTAB5_SD3<22, 0, (outs vrrc:$VRT),
                                 (ins vrrc:$VRA, vrrc:$VRB, u3imm:$SH),
                                 "vsldbi $VRT, $VRA, $VRB, $SH",
                                 IIC_VecGeneral, 
                                 [(set v16i8:$VRT,
                                       (int_ppc_altivec_vsldbi v16i8:$VRA,
                                                               v16i8:$VRB,
-                                                              i32:$SH))]>;
+                                                              timm:$SH))]>;
   def VSRDBI : VNForm_VTAB5_SD3<22, 1, (outs vrrc:$VRT),
                                 (ins vrrc:$VRA, vrrc:$VRB, u3imm:$SH),
                                 "vsrdbi $VRT, $VRA, $VRB, $SH",
                                 IIC_VecGeneral,
                                 [(set v16i8:$VRT,
                                       (int_ppc_altivec_vsrdbi v16i8:$VRA,
                                                               v16i8:$VRB, 
-                                                              i32:$SH))]>;
+                                                              timm:$SH))]>;
   defm VSTRIBR : VXForm_VTB5_RCr<13, 1, (outs vrrc:$vT), (ins vrrc:$vB),
                                  "vstribr", "$vT, $vB", IIC_VecGeneral,
          [(set v16i8:$vT,
                                        (int_ppc_altivec_vstribr v16i8:$vB))]>;
   defm VSTRIBL : VXForm_VTB5_RCr<13, 0, (outs vrrc:$vT), (ins vrrc:$vB),
                                  "vstribl", "$vT, $vB", IIC_VecGeneral,
                                  [(set v16i8:$vT,
                                        (int_ppc_altivec_vstribl v16i8:$vB))]>;