x86: use something common for both architectures.

Using explicit hexa (0xFFFFFFUL) introduces an unnecessary difference
between i386 and x86_64 because of the size of their long. Use -1UL instead.
Signed-off-by: NGlauber Costa <gcosta@redhat.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

include/asm-x86/uaccess_32.h

@@ -25,7 +25,7 @@
 #define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
 
 
-#define KERNEL_DS	MAKE_MM_SEG(0xFFFFFFFFUL)
+#define KERNEL_DS	MAKE_MM_SEG(-1UL)
 #define USER_DS		MAKE_MM_SEG(PAGE_OFFSET)
 
 #define get_ds()	(KERNEL_DS)

include/asm-x86/uaccess_64.h

@@ -22,7 +22,7 @@
 
 #define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
 
-#define KERNEL_DS	MAKE_MM_SEG(0xFFFFFFFFFFFFFFFFUL)
+#define KERNEL_DS	MAKE_MM_SEG(-1UL)
 #define USER_DS		MAKE_MM_SEG(PAGE_OFFSET)
 
 #define get_ds()	(KERNEL_DS)