gpu: nvgpu: Cleanup for gr_gk20a header

Removed unused struct from gr_gk20a.h
Change static allocation for struct gr_gk20a to dynamic type.
Change all the files that being affected by that change.

Call gr allocation from corresponding init_support functions, which
are part of the probe functions.
nvgpu_pci_init_support in pci.c
vgpu_init_support in vgpu_linux.c
gk20a_init_support in module.c

Call gr free before the gk20a free call in nvgpu_free_gk20a.

Rename struct gr_gk20a to struct nvgpu_gr

JIRA NVGPU-3132

Change-Id: Ief5e664521f141c7378c4044ed0df5f03ba06fca
Signed-off-by: Vinod G <vinodg@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/2095798
Reviewed-by: Seshendra Gadagottu <sgadagottu@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/os/linux/driver_common.c

@@ -309,6 +309,9 @@ static void nvgpu_free_gk20a(struct gk20a *g)
 {
 	struct nvgpu_os_linux *l = nvgpu_os_linux_from_gk20a(g);
 
+	/* free gr memory */
+	nvgpu_gr_free(g);
+
 	kfree(l);
 }