drm/gma500: remove trailing whitespaces

Remove trailing whitespaces.  No functional change.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210419081807.68000-2-krzysztof.kozlowski@canonical.com