fdt: Add INT32_MAX to kernel.h for libfdt

Unfortunately libfdt needs this value now, which is present in the
stdint.h header. That file is just a placeholder in U-Boot and these sorts
of constants appear in the linux/kernel.h header instead.

To keep libfdt happy, add INT32_MAX too.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

include/linux/kernel.h

@@ -37,6 +37,8 @@
 #define UINT32_MAX	U32_MAX
 #define UINT64_MAX	U64_MAX
 
+#define INT32_MAX	S32_MAX
+
 #define STACK_MAGIC	0xdeadbeef
 
 #define REPEAT_BYTE(x)	((~0ul / 0xff) * (x))