drm/dp: Remove a gratuituous blank line

It's idiomatic to check the return value of a function call immediately
after the function call, without any blank lines in between, to make it
more obvious that the two lines belong together.

Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191021143437.1477719-3-thierry.reding@gmail.com