NTB: disable x86_32 support

Atomic readq and writeq do not exist by default on some 32bit
architectures, thus causing compile errors due to non-existent symbols.
Since NTB has not been tested 32bit, disable x86_32 support until such
time as this and any other issues can be properly discovered.
Signed-off-by: Jon Mason <jon.mason@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/ntb/Kconfig

 config NTB
        tristate "Intel Non-Transparent Bridge support"
        depends on PCI
-       depends on X86
+       depends on X86_64
        help
         The PCI-E Non-transparent bridge hardware is a point-to-point PCI-E bus
         connecting 2 systems.  When configured, writes to the device's PCI