Currently, I am on T2 General visa and my employer has put me on Gardening leave which ends on 10th August. They are notifying UKBA about the change of circumstances of my gardening leave now and then they will inform them again on 10th August about the termination of my employment. My question is- can I travel out of the UK and return back during my gardening leave?
Yes, you can come and go, right up until the time of curtailment of your Tier 2 visa. Upon curtailment by UKVI, you would be notified of the period of time in which you have to leave the UK. (UKBA was superseded by UK Visa and Immigration in 2013).
As you note, you were given 90-days notice, and that your employer informed UKVI at the same time. Once UKVI is notified of the Change of Circumstances, it will then curtail your leave from the date of its decision.
Take care, however, as you do: during garden leave, you continue to be fully bound by your employment conditions and you may need to notify your employer of your plans, or lack of availability by absence from the country.