Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/mm/highmem.c b/mm/highmem.c
index 59db322..107b10f 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -105,9 +105,8 @@
 }
 #endif
 
-unsigned long totalhigh_pages __read_mostly;
-EXPORT_SYMBOL(totalhigh_pages);
-
+atomic_long_t _totalhigh_pages __read_mostly;
+EXPORT_SYMBOL(_totalhigh_pages);
 
 EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);