Double arm/timer internal test timeout

Change-Id: I1b55503ef1068ffa836b75b695bdbb8ae94c6aa1
diff --git a/arm/unittests.cfg b/arm/unittests.cfg
index f776b66..5e53212 100644
--- a/arm/unittests.cfg
+++ b/arm/unittests.cfg
@@ -225,7 +225,7 @@
 [timer]
 file = timer.flat
 groups = timer
-timeout = 10s
+timeout = 20s
 arch = arm64
 
 # Exit tests