[compiler/tflite2circle] Introduce Sign operation (#16388)

This adds support for the Sign operation in tflite2circle.

ONE-DCO-1.0-Signed-off-by: Seungho Henry Park <shs.park@samsung.com>

Author: shs-park

compiler/tflite2circle/src/TFLOperator.lst

@@ -153,3 +153,4 @@ TFL_OPERATOR(BROADCAST_ARGS)
 TFL_OPERATOR(RANDOM_STANDARD_NORMAL)
 TFL_OPERATOR(GELU)
 TFL_OPERATOR(RELU_0_TO_1)
+TFL_OPERATOR(SIGN)