[PATCH] make-event-names.py: fix SYN_MAX definition for modern kernel headers

SYN_MAX has been exported to user space since 3.12 (52764fed5: Input: add
SYN_MAX and SYN_CNT constants), so only define it locally if not already
defined, otherwise the build breaks.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
 src/make-event-names.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/make-event-names.py b/src/make-event-names.py
index bc77f2c..2d0924d 100755
--- a/src/make-event-names.py
+++ b/src/make-event-names.py
@@ -92,7 +92,9 @@ def print_mapping_table(bits):
 	print("#ifndef EVENT_NAMES_H")
 	print("#define EVENT_NAMES_H")
 	print("")
+	print("#ifndef SYN_MAX")
 	print("#define SYN_MAX 3 /* linux/input.h doesn't define that */")
+	print("#endif")
 	print("")
 
 	for prefix in prefixes: