msm: kgsl: Fix typecasting issue in kgsl_cma_coherent_free()

The attrs variable is value which is passed to dma_free_attrs()
along with the host pointer. Currently attrs value is assigned
to address of memdesc->attrs which can result into a memory
leak due to incorrect attribute value. So fix typecasting
issue while assigning attrs value.

Change-Id: I369314b1ce640bd7b3b3d063d95268f4e9819b8c
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>