ANDROID: GKI: add allowed list for Exynosauto SoC

This patch adds GKI symbol list for Exynosauto SoC. We need to add
below 3 function symbols and it required by DRM(Direct Rendering Manager)
driver.

3 function symbol(s) added
  'void display_timings_release(struct display_timings*)'
  'struct display_timings* of_get_display_timings(const struct device_node*)'
  'int videomode_from_timings(const struct display_timings*, struct videomode*, unsigned int)'

Bug: 305126879
Change-Id: Ieaf3b82e18c0a3a90c274ed752af8ed84df5c150
Signed-off-by: Hoyoung Lee <hy_fifty.lee@samsung.com>