drm/amdgpu: Fix kcalloc over kzalloc in 'gmc_v9_0_init_mem_ranges'

Replace kzalloc(n * sizeof(...), ...) with kcalloc(n, sizeof(...), ...)
since kcalloc is the preferred API in case of allocating with multiply.

Fixes the below:

WARNING: Prefer kcalloc over kzalloc with multiply

Cc: Guchun Chen <guchun.chen@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>