[NFC][PowerPC] Merge ppc64 encoding error tests (llvm#169669)

Based on the RUN lines, there is actually no need for different versions
of these error files since no cpu specific
option needed. Combine to reduce confusion and maintenance as these are
not huge files.

Author: lei137

llvm/test/MC/PowerPC/ppc64-encoding-ISA31-errors.s

@@ -4,6 +4,71 @@
 # RUN: not llvm-mc -triple powerpc64le-unknown-unknown < %s 2> %t
 # RUN: FileCheck < %t %s
 
+# From ISA31
+
+# CHECK: error: invalid operand for instruction
+paddi 1, 1, 32, 1
+
+# CHECK: error: invalid operand for instruction
+pld 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plbz 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plfd 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plfs 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plha 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plhz 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plwa 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plwz 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plxsd 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plxssp 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+plxv 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstb 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstd 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstfd 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstfs 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+psth 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstw 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstxsd 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstxssp 1, 32(1), 1
+
+# CHECK: error: invalid operand for instruction
+pstxv 1, 32(1), 1
+
 # Register operands
 
 # CHECK: error: invalid operand for instruction