The check is wrong since it would have to check whether the
new iomem region overlaps with an existing region. Checking
for the base address only is not enough.
Currently this is not possible because every device conflicts
with the top iomem region which covers the whole address space.

This at least fixes the regression that devices whose memory region
begins at 0x0 can no longer be succesfully registered.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>