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this should be an adjustable linear voltage regulator AP2204K-ADJTRG1  manufacured by Advanced Analog Circuits (FBCD Semiconductor Manufacturing Limited Shanghai) now part of Diodes Inc. . The capacitors, wide output-trace as well as the feedback network match the pin-out shown in the datasheet.
The RP170N381B also carries code GAF. It is a linear regulator and from the photographs appears to be in the power supply section. To be absolutely sure you need the schematics for the board as codes are often duplicated by several manufacturers.