xf86drm: include <limits.h> for PATH_MAX

fixes compilation error with musl libc and Solaris based platforms.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92082
Signed-off-by: Felix Janda <felix.janda@posteo.de>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
diff --git a/xf86drm.c b/xf86drm.c
index a9f5c29..c1cab1b 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -45,6 +45,7 @@
 #include <stddef.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <limits.h>
 #include <signal.h>
 #include <time.h>
 #include <sys/types.h>