drm/amdgpu: Clean up errors in amdgpu_drv.c

Fix the following errors reported by checkpatch:

ERROR: do not initialise globals to 0
Signed-off-by: chenxuebing <chenxb_99091@126.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -593,7 +593,7 @@ module_param_named(timeout_period, amdgpu_watchdog_timer.period, uint, 0644);
 #ifdef CONFIG_DRM_AMDGPU_SI
 
 #if IS_ENABLED(CONFIG_DRM_RADEON) || IS_ENABLED(CONFIG_DRM_RADEON_MODULE)
-int amdgpu_si_support = 0;
+int amdgpu_si_support;
 MODULE_PARM_DESC(si_support, "SI support (1 = enabled, 0 = disabled (default))");
 #else
 int amdgpu_si_support = 1;
@@ -612,7 +612,7 @@ module_param_named(si_support, amdgpu_si_support, int, 0444);
 #ifdef CONFIG_DRM_AMDGPU_CIK
 
 #if IS_ENABLED(CONFIG_DRM_RADEON) || IS_ENABLED(CONFIG_DRM_RADEON_MODULE)
-int amdgpu_cik_support = 0;
+int amdgpu_cik_support;
 MODULE_PARM_DESC(cik_support, "CIK support (1 = enabled, 0 = disabled (default))");
 #else
 int amdgpu_cik_support = 1;