drm/ttm_bo_api: update the description for @placement and @sg

Correct the argument name of @placement and added @sg description for
ttm_bo_init() and ttm_bo_init_reserved().

Argument @flags was replaced to @placement by Jerome in commit
09855ac

Argument @sg was added by Dave in commit
129b78b

Signed-off-by: Amos Kong <amos@sietium.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/38eac09bf2ddd6088cc8a126e6bc4792eaa2dc88.1633462176.git.amos@sietium.com
Signed-off-by: Christian König <christian.koenig@amd.com>

include/drm/ttm/ttm_bo_api.h

@@ -351,9 +351,10 @@ bool ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
  * @bo: Pointer to a ttm_buffer_object to be initialized.
  * @size: Requested size of buffer object.
  * @type: Requested type of buffer object.
- * @flags: Initial placement flags.
+ * @placement: Initial placement for buffer object.
  * @page_alignment: Data alignment in pages.
  * @ctx: TTM operation context for memory allocation.
+ * @sg: Scatter-gather table.
  * @resv: Pointer to a dma_resv, or NULL to let ttm allocate one.
  * @destroy: Destroy function. Use NULL for kfree().
  *
@@ -394,14 +395,15 @@ int ttm_bo_init_reserved(struct ttm_device *bdev,
  * @bo: Pointer to a ttm_buffer_object to be initialized.
  * @size: Requested size of buffer object.
  * @type: Requested type of buffer object.
- * @flags: Initial placement flags.
+ * @placement: Initial placement for buffer object.
  * @page_alignment: Data alignment in pages.
  * @interruptible: If needing to sleep to wait for GPU resources,
  * sleep interruptible.
  * pinned in physical memory. If this behaviour is not desired, this member
  * holds a pointer to a persistent shmem object. Typically, this would
  * point to the shmem object backing a GEM object if TTM is used to back a
  * GEM user interface.
+ * @sg: Scatter-gather table.
  * @resv: Pointer to a dma_resv, or NULL to let ttm allocate one.
  * @destroy: Destroy function. Use NULL for kfree().
  *