AMDGPU: Remove incorrect uses of SubtaretPredicate around DS_Reals (#85001)

SubtargetPredicate is copied from DS_Pseudo to DS_Real. We should not
use another SubtargetPredicate assignment around DS_Real, because doing
so will override the predicate from DS_Pseudo.

For example, for DS_ADD_RTN_F64, SubtargetPredicate was set to
HasLdsAtomicAddF64 in Pseudo. And it will be overridden to isGFX90APlus
if we assign isGFX90APlus to SubtargetPredicate in Real definition.

Author: changpeng

llvm/lib/Target/AMDGPU/DSInstructions.td

@@ -1735,14 +1735,12 @@ def DS_WRITE_B128_vi      : DS_Real_vi<0xdf, DS_WRITE_B128>;
 def DS_READ_B96_vi        : DS_Real_vi<0xfe, DS_READ_B96>;
 def DS_READ_B128_vi       : DS_Real_vi<0xff, DS_READ_B128>;
 
-let SubtargetPredicate = isGFX90APlus in {
-  def DS_ADD_F64_vi     : DS_Real_vi<0x5c, DS_ADD_F64>;
-  def DS_ADD_RTN_F64_vi : DS_Real_vi<0x7c, DS_ADD_RTN_F64>;
-} // End SubtargetPredicate = isGFX90APlus
-
-let SubtargetPredicate = isGFX940Plus in {
-  def DS_PK_ADD_F16_vi     : DS_Real_vi<0x17, DS_PK_ADD_F16>;
-  def DS_PK_ADD_RTN_F16_vi : DS_Real_vi<0xb7, DS_PK_ADD_RTN_F16>;
-  def DS_PK_ADD_BF16_vi     : DS_Real_vi<0x18, DS_PK_ADD_BF16>;
-  def DS_PK_ADD_RTN_BF16_vi : DS_Real_vi<0xb8, DS_PK_ADD_RTN_BF16>;
-} // End SubtargetPredicate = isGFX940Plus
+// GFX90A+.
+def DS_ADD_F64_vi     : DS_Real_vi<0x5c, DS_ADD_F64>;
+def DS_ADD_RTN_F64_vi : DS_Real_vi<0x7c, DS_ADD_RTN_F64>;
+
+// GFX940+.
+def DS_PK_ADD_F16_vi     : DS_Real_vi<0x17, DS_PK_ADD_F16>;
+def DS_PK_ADD_RTN_F16_vi : DS_Real_vi<0xb7, DS_PK_ADD_RTN_F16>;
+def DS_PK_ADD_BF16_vi     : DS_Real_vi<0x18, DS_PK_ADD_BF16>;
+def DS_PK_ADD_RTN_BF16_vi : DS_Real_vi<0xb8, DS_PK_ADD_RTN_BF16>;