msm: kgsl: Add macrotiling channels property

This change retrieves number of macrotiling channels from
device tree, configures the RBBM hardware accordingly, and
passes it to user as a property.

Change-Id: I8dce177451e7e2c0dd29dc9a91e99f0e63895a96
Signed-off-by: Hai Li <hali@codeaurora.org>