Distribute linux/aarch64/arch_regs.h

* Makefile.am (EXTRA_DIST): Add linux/aarch64/arch_regs.h.
diff --git a/Makefile.am b/Makefile.am
index 2030f9b..48fe1d7 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -164,6 +164,7 @@
 	linux/32/syscallent.h		\
 	linux/64/ioctls_inc.h		\
 	linux/64/syscallent.h		\
+	linux/aarch64/arch_regs.h	\
 	linux/aarch64/errnoent1.h	\
 	linux/aarch64/ioctls_arch0.h	\
 	linux/aarch64/ioctls_arch1.h	\