[mlir] Fix declaration of nano time function in benchmark infra

[shabalin]

Summary

In d4555698f89af373f43dcb4aa1587231496bcd31, the name of nano precision timer function has changed from nano_time to nanoTime, but benchmarks were not updated to reflect that. This change addresses the discrepancy.

[ftynse]

Could you please reference the commit that changed the function name in the description of this commit?

[shabalin]

Update commit message to refer to the prior commit, as requested.

mlir/benchmark/python/common.py

def get_kernel_func_from_module(module: ir.Module) -> func.FuncOp:
     assert len(module.operation.regions[0].blocks) == 1, \
         "Expected kernel module to have only one block"
     assert len(module.operation.regions[0].blocks[0].operations) == 1, \
         "Expected kernel module to have only one operation"
     return module.operation.regions[0].blocks[0].operations[0]
 
 
 def emit_timer_func() -> func.FuncOp:
-    """Returns the declaration of nano_time function. If nano_time function is
+    """Returns the declaration of nanoTime function. If nanoTime function is
     used, the `MLIR_RUNNER_UTILS` and `MLIR_C_RUNNER_UTILS` must be included.
     """
     i64_type = ir.IntegerType.get_signless(64)
-    nano_time = func.FuncOp(
-        "nano_time", ([], [i64_type]), visibility="private")
-    nano_time.attributes["llvm.emit_c_interface"] = ir.UnitAttr.get()
-    return nano_time
+    nanoTime = func.FuncOp(
+        "nanoTime", ([], [i64_type]), visibility="private")
+    nanoTime.attributes["llvm.emit_c_interface"] = ir.UnitAttr.get()
+    return nanoTime
 
 
 def emit_benchmark_wrapped_main_func(func, timer_func):
     """Takes a function and a timer function, both represented as FuncOp
     objects, and returns a new function. This new function wraps the call to
     the original function between calls to the timer_func and this wrapping
     in turn is executed inside a loop. The loop is executed
     len(func.type.results) times. This function can be used to create a