[benchmark] [PowerPC] Rename mftbl to mftb

[stevewan]

Summary

mftb and mftbl are equivalent, yet mftbl is not recognized on AIX. Therefore, rename mftbl to only have mftb.

This mirrors https://reviews.llvm.org/D89506 in LLVM monorepo.

[stevewan]

Committed in https://github.com/llvm/llvm-test-suite/commit/4af296ef47a0a9314a9c3ca65bf3c5d4c7020451.

MicroBenchmarks/libs/benchmark-1.3.0/CONTRIBUTORS

 Pascal Leroy <[e-mail]>
 Paul Redmond <[e-mail]>
 Pierre Phaneuf <[e-mail]>
 Radoslav Yovchev <[e-mail]>
 Raul Marin <[e-mail]>
 Ray Glover <[e-mail]>
 Roman Lebedev <[e-mail]>
 Shuo Chen <[e-mail]>
+Steven Wan <[e-mail]>
 Tobias Ulvgård <[e-mail]>
 Tom Madams <[e-mail]> <[e-mail]>
 Yixuan Qiu <[e-mail]>
 Yusuke Suzuki <[e-mail]>
 Zbigniew Skowron <[e-mail]>
 Min-Yih Hsu <[e-mail]>

MicroBenchmarks/libs/benchmark-1.3.0/README.llvm

 * https://github.com/google/benchmark/commit/a77d5f70efaebe2b7e8c10134526a23a7ce7ef35
   and
   https://github.com/google/benchmark/commit/ecc1685340f58f7fe6b707036bc0bb1fccabb0c1
   are applied on top of v1.3.0 to fix timestamp-related inline asm issues and
   32-bit RISC-V build failures. The second cherrypicked commit fixes formatting
   issues introduced by the first one.
 * https://github.com/google/benchmark/commit/ffe1342eb2faa7d2e7c35b4db2ccf99fab81ec20
   is applited on top of v1.3.0 to add the CycleTimer implementation for M680x0
+* https://github.com/google/benchmark/commit/d9abf017632be4a00b92cf4289539b353fcea5d2
+  is applied on top of v1.3.0 to rename 'mftbl' to 'mftb'.

MicroBenchmarks/libs/benchmark-1.3.0/src/cycleclock.h

 #if defined(__powerpc64__) || defined(__ppc64__)
   int64_t tb;
   asm volatile("mfspr %0, 268" : "=r"(tb));
   return tb;
 #else
   uint32_t tbl, tbu0, tbu1;
   asm volatile(
       "mftbu %0\n"
-      "mftbl %1\n"
+      "mftb %1\n"
       "mftbu %2"
       : "=r"(tbu0), "=r"(tbl), "=r"(tbu1));
   tbl &= -static_cast<int32_t>(tbu0 == tbu1);
   // high 32 bits in tbu1; low 32 bits in tbl  (tbu0 is no longer needed)
   return (static_cast<uint64_t>(tbu1) << 32) | tbl;
 #endif
 #elif defined(__sparc__)
   int64_t tick;