UML is a bit special since it does not have iomem nor dma.  That means a
lot of drivers will not build if they miss a dependency on HAS_IOMEM.
s390 used to have the same issues but since it gained PCI support UML is
the only stranger.

We are tired of patching dozens of new drivers after every merge window
just to un-break allmod/yesconfig UML builds.  One could argue that a
decent driver has to know on what it depends and therefore a missing
HAS_IOMEM dependency is a clear driver bug.  But the dependency not
obvious and not everyone does UML builds with COMPILE_TEST enabled when
developing a device driver.

A possible solution to make these builds succeed on UML would be
providing stub functions for ioremap() and friends which fail upon
runtime.  Another one is simply disabling COMPILE_TEST for UML.  Since
it is the least hassle and does not force use to fake iomem support
let's do the latter.

Link: http://lkml.kernel.org/r/1466152995-28367-1-git-send-email-richard@nod.atSigned-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>