alpha: switch to generic sigaltstack

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 7e3710c..9d5904c 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -22,6 +22,7 @@
 	select GENERIC_STRNLEN_USER
 	select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_RELA
+	select GENERIC_SIGALTSTACK
 	help
 	  The Alpha is a 64-bit general-purpose processor designed and
 	  marketed by the Digital Equipment Corporation of blessed memory,