arm64: switch to generic compat rt_sigprocmask()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index d9c901d..4b99d63 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -6,6 +6,7 @@
 	select CLONE_BACKWARDS
 	select COMMON_CLK
 	select GENERIC_CLOCKEVENTS
+	select GENERIC_COMPAT_RT_SIGPROCMASK
 	select GENERIC_HARDIRQS_NO_DEPRECATED
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_PROBE