drm/vmwgfx/vmwgfx_shader: Demote kernel-doc abuses and fix-up worthy headers

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/vmwgfx/vmwgfx_shader.c:134: warning: Function parameter or member 'res' not described in 'vmw_res_to_shader'
 drivers/gpu/drm/vmwgfx/vmwgfx_shader.c:663: warning: Function parameter or member 'base' not described in 'vmw_user_shader_base_to_res'
 drivers/gpu/drm/vmwgfx/vmwgfx_shader.c:695: warning: Function parameter or member 'p_base' not described in 'vmw_user_shader_base_release'
 drivers/gpu/drm/vmwgfx/vmwgfx_shader.c:965: warning: Function parameter or member 'dev_priv' not described in 'vmw_compat_shader_add'
 drivers/gpu/drm/vmwgfx/vmwgfx_shader.c:965: warning: Function parameter or member 'size' not described in 'vmw_compat_shader_add'
 drivers/gpu/drm/vmwgfx/vmwgfx_shader.c:965: warning: Excess function parameter 'tfile' description in 'vmw_compat_shader_add'

Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115181313.3431493-37-lee.jones@linaro.org

drivers/gpu/drm/vmwgfx/vmwgfx_shader.c

@@ -125,7 +125,7 @@ static const struct vmw_res_func vmw_dx_shader_func = {
 	.commit_notify = vmw_dx_shader_commit_notify,
 };
 
-/**
+/*
  * Shader management:
  */
 
@@ -654,7 +654,7 @@ out_resource_init:
 
 
 
-/**
+/*
  * User-space shader management:
  */
 
@@ -686,7 +686,7 @@ static void vmw_shader_free(struct vmw_resource *res)
 			    vmw_shader_size);
 }
 
-/**
+/*
  * This function is called when user space has no more references on the
  * base object. It releases the base-object's reference on the resource object.
  */
@@ -945,13 +945,13 @@ int vmw_shader_remove(struct vmw_cmdbuf_res_manager *man,
  * vmw_compat_shader_add - Create a compat shader and stage it for addition
  * as a command buffer managed resource.
  *
+ * @dev_priv: Pointer to device private structure.
  * @man: Pointer to the compat shader manager identifying the shader namespace.
  * @user_key: The key that is used to identify the shader. The key is
  * unique to the shader type.
  * @bytecode: Pointer to the bytecode of the shader.
  * @shader_type: Shader type.
- * @tfile: Pointer to a struct ttm_object_file that the guest-backed shader is
- * to be created with.
+ * @size: Command size.
  * @list: Caller's list of staged command buffer resource actions.
  *
  */