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>

drivers/firmware/Kconfig

@@ -108,6 +108,9 @@ config DMI_SYSFS
 	  under /sys/firmware/dmi when this option is enabled and
 	  loaded.
 
+config DMI_SCAN_MACHINE_NON_EFI_FALLBACK
+	bool
+
 config ISCSI_IBFT_FIND
 	bool "iSCSI Boot Firmware Table Attributes"
 	depends on X86