[SEPolicy] Name GPU service back to "gpu"

Changed the GPU service name back to be compatible with external
engines/tools' usage of vkjson cmd.

Bug: 118347356
Test: adb shell cmd gpu vkjson
Change-Id: Ie432fd8be63d33070ad037c509467c8367b42d39

private/service_contexts

@@ -62,7 +62,7 @@ font                                      u:object_r:font_service:s0
 android.hardware.fingerprint.IFingerprintDaemon u:object_r:fingerprintd_service:s0
 gfxinfo                                   u:object_r:gfxinfo_service:s0
 graphicsstats                             u:object_r:graphicsstats_service:s0
-gpuservice                                u:object_r:gpu_service:s0
+gpu                                       u:object_r:gpu_service:s0
 hardware                                  u:object_r:hardware_service:s0
 hardware_properties                       u:object_r:hardware_properties_service:s0
 hdmi_control                              u:object_r:hdmi_control_service:s0