SDL: Fixed build with older Linux kernel headers

SDL Commits
1 
From ebed961cb2f685a6db9467f2496d644110bea3c3 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Thu, 11 Nov 2021 09:51:39 -0800
Subject: [PATCH] Fixed build with older Linux kernel headers

---
 src/joystick/linux/SDL_sysjoystick.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/joystick/linux/SDL_sysjoystick.c b/src/joystick/linux/SDL_sysjoystick.c
index a5e80d6044..9172165768 100644
--- a/src/joystick/linux/SDL_sysjoystick.c
+++ b/src/joystick/linux/SDL_sysjoystick.c
@@ -56,6 +56,12 @@
 #ifndef SYN_DROPPED
 #define SYN_DROPPED 3
 #endif
+#ifndef BTN_NORTH
+#define BTN_NORTH       0x133
+#endif
+#ifndef BTN_WEST
+#define BTN_WEST        0x134
+#endif
 #ifndef BTN_DPAD_UP
 #define BTN_DPAD_UP     0x220
 #endif