x86/sfi: Enable enumeration of SD devices

SFI specification v0.8.2 defines type of devices which are connected to
SD bus. In particularly WiFi dongle is a such.

Add a callback to enumerate the devices connected to SD bus.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1468322192-62080-1-git-send-email-andriy.shevchenko@linux.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>