Revert "msm: kgsl: Return error if the user allocates a buffer size of zero"

This reverts commit b4c2bdeb62c40c98668d35281ac20f13399b1644.
Revert "msm: kgsl: Enable "big page" memory allocations"

This reverts commit a82b1371e913e3901493bc72d8407d40f3da96b1.