drm/gma500: clean up indentation issues

There are a couple of statements that are indented too deeply,
remove the extraneous tabs and also an empty line.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200920141407.32672-1-colin.king@canonical.com