Cycles: OpenCL split kernel cleanup, move casts from .h files to .cl files

Ideally we shouldn't use char* at all, but for now we have to, so at least
let's assume common .h files are free from pointer magic.

intern/cycles/kernel/split/kernel_data_init.h

@@ -51,9 +51,9 @@
  * The number of elements in the queues is initialized to 0;
  */
 ccl_device void kernel_data_init(
-        ccl_global char *globals,
-        ccl_global char *shader_data_sd,                  /* Arguments related to ShaderData */
-        ccl_global char *shader_data_sd_DL_shadow,        /* Arguments related to ShaderData */
+        KernelGlobals *kg,
+        ShaderData *sd,
+        ShaderData *sd_DL_shadow,
 
         ccl_global float3 *P_sd,
         ccl_global float3 *P_sd_DL_shadow,
@@ -175,19 +175,11 @@ ccl_device void kernel_data_init(
 #endif
         int parallel_samples)                        /* Number of samples to be processed in parallel */
 {
-
-	/* Load kernel globals structure */
-	KernelGlobals *kg = (KernelGlobals *)globals;
-
 	kg->data = data;
 #define KERNEL_TEX(type, ttype, name) \
 	kg->name = name;
 #include "../kernel_textures.h"
 
-	/* Load ShaderData structure */
-	ShaderData *sd = (ShaderData *)shader_data_sd;
-	ShaderData *sd_DL_shadow = (ShaderData *)shader_data_sd_DL_shadow;
-
 	sd->P = P_sd;
 	sd_DL_shadow->P = P_sd_DL_shadow;