drm/vmwgfx: Fix NULL pointer comparison

Replace direct comparisons to NULL i.e.
'x == NULL' with '!x'. As per coding standard.

Signed-off-by: Ravikant B Sharma <ravikant.s2@samsung.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_shader.c b/drivers/gpu/drm/vmwgfx/vmwgfx_shader.c
index 92f8b1d..55788e9 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_shader.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_shader.c
@@ -750,7 +750,7 @@ static int vmw_user_shader_alloc(struct vmw_private *dev_priv,
 	}
 
 	ushader = kzalloc(sizeof(*ushader), GFP_KERNEL);
-	if (unlikely(ushader == NULL)) {
+	if (unlikely(!ushader)) {
 		ttm_mem_global_free(vmw_mem_glob(dev_priv),
 				    vmw_user_shader_size);
 		ret = -ENOMEM;
@@ -820,7 +820,7 @@ static struct vmw_resource *vmw_shader_alloc(struct vmw_private *dev_priv,
 	}
 
 	shader = kzalloc(sizeof(*shader), GFP_KERNEL);
-	if (unlikely(shader == NULL)) {
+	if (unlikely(!shader)) {
 		ttm_mem_global_free(vmw_mem_glob(dev_priv),
 				    vmw_shader_size);
 		ret = -ENOMEM;
@@ -980,7 +980,7 @@ int vmw_compat_shader_add(struct vmw_private *dev_priv,
 
 	/* Allocate and pin a DMA buffer */
 	buf = kzalloc(sizeof(*buf), GFP_KERNEL);
-	if (unlikely(buf == NULL))
+	if (unlikely(!buf))
 		return -ENOMEM;
 
 	ret = vmw_dmabuf_init(dev_priv, buf, size, &vmw_sys_ne_placement,