gpu: nvgpu: moved & renamed "struct pmu_gk20a"

- Renamed "struct pmu_gk20a" to "struct nvgpu_pmu" then moved
to file "pmu.h" under folder "drivers/gpu/nvgpu/include/nvgpu/"

- Included header file "pmu.h" to dependent file &
removed "pmu_gk20a.h" include if its usage is not present.

- Replaced "struct pmu_gk20a" with "struct nvgpu_pmu" in dependent
source & header files.

JIRA NVGPU-56

Change-Id: Ia3c606616831027093d5c216959c6a40d7c2632e
Signed-off-by: Mahantesh Kumbar <mkumbar@nvidia.com>
Reviewed-on: http://git-master/r/1479209
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/clk/clk_prog.c

@@ -12,7 +12,6 @@
  */
 
 #include <nvgpu/bios.h>
-
 #include <nvgpu/kmem.h>
 
 #include "gk20a/gk20a.h"
@@ -24,7 +23,6 @@
 #include "gm206/bios_gm206.h"
 #include "ctrl/ctrlclk.h"
 #include "ctrl/ctrlvolt.h"
-#include "gk20a/pmu_gk20a.h"
 
 static struct clk_prog *construct_clk_prog(struct gk20a *g, void *pargs);
 static u32 devinit_get_clk_prog_table(struct gk20a *g,