drm/gma500/power: Remove excess param description 'state'

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

 drivers/gpu/drm/gma500/power.c:190: warning: Excess function parameter 'state' description in 'gma_power_suspend'

Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Benjamin Defnet <benjamin.r.defnet@intel.com>
Cc: Rajesh Poornachandran <rajesh.poornachandran@intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115181313.3431493-39-lee.jones@linaro.org