drm/radeon/radeon_cs: Fix a bunch of doc-rot issues

drm/radeon/radeon_cs: Fix a bunch of doc-rot issues

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

 drivers/gpu/drm/radeon/radeon_cs.c:416: warning: Function parameter or member 'backoff' not described in 'radeon_cs_parser_fini'
 drivers/gpu/drm/radeon/radeon_cs.c:735: warning: Function parameter or member 'p' not described in 'radeon_cs_packet_parse'
 drivers/gpu/drm/radeon/radeon_cs.c:735: warning: Function parameter or member 'idx' not described in 'radeon_cs_packet_parse'
 drivers/gpu/drm/radeon/radeon_cs.c:735: warning: Excess function parameter 'parser' description in 'radeon_cs_packet_parse'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Function parameter or member 'p' not described in 'radeon_cs_packet_next_reloc'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Function parameter or member 'cs_reloc' not described in 'radeon_cs_packet_next_reloc'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Function parameter or member 'nomm' not described in 'radeon_cs_packet_next_reloc'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Excess function parameter 'parser' description in 'radeon_cs_packet_next_reloc'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Excess function parameter 'data' description in 'radeon_cs_packet_next_reloc'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Excess function parameter 'offset_start' description in 'radeon_cs_packet_next_reloc'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Excess function parameter 'offset_mask' description in 'radeon_cs_packet_next_reloc'
 drivers/gpu/drm/radeon/radeon_cs.c:844: warning: Excess function parameter 'reloc' description in 'radeon_cs_packet_next_reloc'

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Jerome Glisse <glisse@freedesktop.org>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>