x86, kexec: Remove 1024G limitation for kexec buffer on 64bit

Now 64bit kernel supports more than 1T ram and kexec tools
could find buffer above 1T, remove that obsolete limitation.
and use MAXMEM instead.

Tested on system with more than 1024G ram.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1359058816-7615-22-git-send-email-yinghai@kernel.org
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/kexec.h

@@ -48,11 +48,11 @@
 # define vmcore_elf_check_arch_cross(x) ((x)->e_machine == EM_X86_64)
 #else
 /* Maximum physical address we can use pages from */
-# define KEXEC_SOURCE_MEMORY_LIMIT      (0xFFFFFFFFFFUL)
+# define KEXEC_SOURCE_MEMORY_LIMIT      (MAXMEM-1)
 /* Maximum address we can reach in physical address mode */
-# define KEXEC_DESTINATION_MEMORY_LIMIT (0xFFFFFFFFFFUL)
+# define KEXEC_DESTINATION_MEMORY_LIMIT (MAXMEM-1)
 /* Maximum address we can use for the control pages */
-# define KEXEC_CONTROL_MEMORY_LIMIT     (0xFFFFFFFFFFUL)
+# define KEXEC_CONTROL_MEMORY_LIMIT     (MAXMEM-1)
 
 /* Allocate one page for the pdp and the second for the code */
 # define KEXEC_CONTROL_PAGE_SIZE  (4096UL + 4096UL)