drm/vmwgfx/vmwgfx_binding: Provide some missing param descriptions and remove others

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

 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:340: warning: Function parameter or member 'shader_slot' not described in 'vmw_binding_add'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:340: warning: Function parameter or member 'slot' not described in 'vmw_binding_add'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:376: warning: Function parameter or member 'from' not described in 'vmw_binding_transfer'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:498: warning: Function parameter or member 'to' not described in 'vmw_binding_state_commit'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:498: warning: Excess function parameter 'ctx' description in 'vmw_binding_state_commit'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:498: warning: Excess function parameter 'scrubbed' description in 'vmw_binding_state_commit'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:520: warning: Function parameter or member 'cbs' not described in 'vmw_binding_rebind_all'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:520: warning: Excess function parameter 'ctx' description in 'vmw_binding_rebind_all'
 drivers/gpu/drm/vmwgfx/vmwgfx_binding.c:795: warning: Function parameter or member 'shader_slot' not described in 'vmw_emit_set_sr'

Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: Zack Rusin <zackr@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/20210115181601.3432599-5-lee.jones@linaro.org