drm/amd/powerplay: Remove unneeded cast from memory allocation

Remove casting the values returned by memory allocation function.

Coccinelle emits WARNING:

./drivers/gpu/drm/amd/powerplay/hwmgr/vega20_processpptables.c:893:37-46: WARNING: casting value returned by memory allocation function to (PPTable_t *) is useless.
Signed-off-by: Li Heng <liheng40@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/hwmgr/vega20_processpptables.c

@@ -890,7 +890,7 @@ static int init_powerplay_table_information(
 				power_saving_clock_count);
 	}
 
-	pptable_information->smc_pptable = (PPTable_t *)kmalloc(sizeof(PPTable_t), GFP_KERNEL);
+	pptable_information->smc_pptable = kmalloc(sizeof(PPTable_t), GFP_KERNEL);
 	if (pptable_information->smc_pptable == NULL)
 		return -ENOMEM;