ZEN: Set default max map count to (INT_MAX - 5)

Per [Fedora][1], they intend to change the default max map count for
their distribution to improve OOTB compatibility with games played
through Steam/Proton.  The value they picked comes from the Steam Deck,
which defaults to INT_MAX - MAPCOUNT_ELF_CORE_MARGIN.

Since most ZEN and Liquorix users probably play games, follow Valve's
lead and raise this value to their default.

[1]: https://fedoraproject.org/wiki/Changes/IncreaseVmMaxMapCount

include/linux/mm.h

@@ -191,7 +191,7 @@ static inline void __mm_zero_struct_page(struct page *page)
  * that.
  */
 #define MAPCOUNT_ELF_CORE_MARGIN	(5)
-#define DEFAULT_MAX_MAP_COUNT	(USHRT_MAX - MAPCOUNT_ELF_CORE_MARGIN)
+#define DEFAULT_MAX_MAP_COUNT	(INT_MAX - MAPCOUNT_ELF_CORE_MARGIN)
 
 extern int sysctl_max_map_count;