ANDROID: driver: gpu: drm: fix export symbol types

In commit 310dd4fe8350 ("ANDROID: driver: gpu: drm: add notifier for
panel related events") a number of new symbols were exported, but they
should have been set as a _GPL symbol.

Fix this up by properly changing the export types.

Bug: 139653858
Cc: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I54dbc1f4d41739ab19040563966a6505897734fb