GKI: Revert "drm: samsung: don't set allow_fb_modifiers explicitly"

This reverts commit 8002d50e. This
change broke the display when we tried to add a framebuffer with
modifiers. Let's revert it first and then figure out how to properly get
it set by the core drm driver.

Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I5757c2b61d270fe0a9abd935e025d2524830df19