x86: Do not reserve brk for DMI if it's not going to be used

This will save 64K bytes from memory when loading linux if DMI is
disabled, which is good for embedded systems.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
LKML-Reference: <1265758732-19320-1-git-send-email-cascardo@holoscopio.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/setup.c

@@ -121,7 +121,9 @@
 unsigned long max_low_pfn_mapped;
 unsigned long max_pfn_mapped;
 
+#ifdef CONFIG_DMI
 RESERVE_BRK(dmi_alloc, 65536);
+#endif
 
 unsigned int boot_cpu_id __read_mostly;