Firmware For Download

ATTENTION: the version of your firmware must match with this(15.5.A.1.5) ftf file before proceeding and you will lose all data on phone memory after flashing! if the version doesn't match you'll have to create your own .ftf unlock file for your firmware version.

Follow this post to create your own .ftf file: All sony Xperia Secutity code pattern Remove & full reset in 5sec vitout full flash

Download and install Androxyde Flashtool.

Install drivers from c/flashtool/drivers

Download this and put it in c/flashtool/firmwares

And than flash the file in flasmode (make sure that WIPE is checked). 

I'm not responsible for any damage if occurs do this with your own caution.

Thanks to this post from @jamesjerss it helped me to remove the pattern.