Accelerometer problem in Galaxy S2
The problem is with your phone Accelerometer(not Gyroscopre). If it is not a hardware problem then Try Restart your phone.
Go to "Settings"-> "Motion" -> "Sensitivity Settings" -> Calibration ->calibrate.
 It automatically calibrates the screen and the gyro sensor. 

IF the problem exist, backup all your things &amp; Restore your phone to factory settings. 

NOTE : Make sure you keep the device on a flat surface and phone screen facing upwards when calibrating the sensor as it gives better results.