limits.h: Include page.h when relying on PAGE_SIZE

limits.h relies on PAGE_SIZE being defined without actually including
page.h. Make sure this is included to avoid compilation failures.

Signed-off-by: Arun Raghavan <arun.raghavan@collabora.co.uk>
diff --git a/libc/include/limits.h b/libc/include/limits.h
index 1de8ea6..d691a8f 100644
--- a/libc/include/limits.h
+++ b/libc/include/limits.h
@@ -90,6 +90,7 @@
 #endif
 
 #ifndef PAGESIZE
+#include <asm/page.h>
 #define  PAGESIZE  PAGE_SIZE
 #endif