drm/amdgpu: add missing header dependencies

We get a few warnings when building kernel with W=1:
drivers/gpu/drm/amd/amdgpu/amdgpu_pll.c:113:6: warning: no previous prototype for 'amdgpu_pll_compute' [-Wmissing-prototypes]
drivers/gpu/drm/amd/amdgpu/cz_smc.c:38:10: warning: no previous prototype for 'cz_get_argument' [-Wmissing-prototypes]
drivers/gpu/drm/amd/amdgpu/cz_smc.c:302:5: warning: no previous prototype for 'cz_smu_start' [-Wmissing-prototypes]
....

In fact, these functions are declared in
drivers/gpu/drm/amd/amdgpu/atombios_i2c.h
drivers/gpu/drm/amd/amdgpu/amdgpu_pll.h
drivers/gpu/drm/amd/amdgpu/cz_dpm.h
drivers/gpu/drm/amd/amdgpu/vi_dpm.h.
So this patch adds missing header dependencies.

Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Baoyou Xie <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_pll.c

···
 #include "amdgpu.h"
 #include "atom.h"
 #include "atombios_encoders.h"
+#include "amdgpu_pll.h"
 #include <asm/div64.h>
 #include <linux/gcd.h>
 

drivers/gpu/drm/amd/amdgpu/atombios_i2c.c

···
 #include "amdgpu.h"
 #include "atom.h"
 #include "amdgpu_atombios.h"
+#include "atombios_i2c.h"
 
 #define TARGET_HW_I2C_CLOCK 50
 

drivers/gpu/drm/amd/amdgpu/cz_smc.c

···
 #include "cz_smumgr.h"
 #include "smu_ucode_xfer_cz.h"
 #include "amdgpu_ucode.h"
+#include "cz_dpm.h"
+#include "vi_dpm.h"
 
 #include "smu/smu_8_0_d.h"
 #include "smu/smu_8_0_sh_mask.h"