This reverts commit 1d84353d.

Because of recent interactions with developers from @umn.edu, all
commits from them have been recently re-reviewed to ensure if they were
correct or not.

Upon review, this commit was found to be incorrect for the reasons
below, so it must be reverted.  It will be fixed up "correctly" in a
later kernel change.

The original commit here, while technically correct, did not fully
handle all of the reported issues that the commit stated it was fixing,
so revert it until it can be "fixed" fully.

Note, ioremap() probably will never fail for old hardware like this, and
if anyone actually used this hardware (a PowerMac era PCI display card),
they would not be using fbdev anymore.

Cc: Kangjie Lu <kjlu@umn.edu>
Cc: Aditya Pakki <pakki001@umn.edu>
Cc: Finn Thain <fthain@telegraphics.com.au>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Fixes: 1d84353d ("video: imsttfb: fix potential NULL pointer dereferences")
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210503115736.2104747-67-gregkh@linuxfoundation.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>