gpu: nvgpu: Add GPU reset to XVE

Add a full GPU reset function to the XVE block. This allows
the driver to reset the GPU (except the XVE and XP interfaces)
to clear the GPU's state.

This is necessary for the GPU rebind to work. The state of the
GPU needs to be cleared before the new driver instance can work.

Bug 1816516

Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/1287642
Reviewed-on: http://git-master/r/1287648
(cherry picked from commit 7e751c0eb2c0f7d9d0b2020600c33fc8b4381878)
Change-Id: Ie2b721bf1b40acbab34de2436dea4e70d33b5611
Reviewed-on: http://git-master/r/1292698
Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

drivers/gpu/nvgpu/gk20a/gk20a.h

@@ -774,6 +774,7 @@ struct gpu_ops {
 		u32 (*xve_readl)(struct gk20a *g, u32 reg);
 		void (*xve_writel)(struct gk20a *g, u32 reg, u32 val);
 		void (*disable_aspm)(struct gk20a *g);
+		void (*reset_gpu)(struct gk20a *g);
 	} xve;
 };