firmware/dmi_scan: generalize for use by other archs

This patch makes a couple of changes to the SMBIOS/DMI scanning
code so it can be used on other archs (such as ARM and arm64):
(a) wrap the calls to ioremap()/iounmap(), this allows the use of a
    flavor of ioremap() more suitable for random unaligned access;
(b) allow the non-EFI fallback probe into hardcoded physical address
    0xF0000 to be disabled.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d3b9186..5aadc49 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -731,6 +731,7 @@
 # The code disables itself when not needed.
 config DMI
 	default y
+	select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
 	bool "Enable DMI scanning" if EXPERT
 	---help---
 	  Enabled scanning of DMI to identify machine quirks. Say Y