msm: kgsl: Specify hang timeout cycles in a6xx_core structure

Hang timeout cycles is the value for the timeout counter to detect
hang at interfaces in the graphics core. As this value is different
for different GPU cores, specify it in a6xx_core structure to allow
per GPU configuration.

Change-Id: I14a93f088531dbf09b125b1ba9ba2005584e6574
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>