Revert "drm/drm_fb_helper: fix fbdev with sparc64"

This reverts commit 4bba72b7 which is
commit 2a1658bf922ffd9b7907e270a7d9cdc9643fc45d upstream.

It breaks the abi of some Android drivers and can be safely reverted as
Android does not currently run on sparc64 systems :)

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I5245629207bf163908a72aeea92495494b71e92c