trusted-firmware.inc: Catch failures on "Booting BL31" stage too

Issue was seen in LTS jobs:
https://tf.validation.linaro.org/scheduler/job/1645072

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I83d01f475ff4bd281883d81de2ca4b924b993d5a
diff --git a/expect-lava/trusted-firmware.inc b/expect-lava/trusted-firmware.inc
index 7fb68bb..2281f3c 100644
--- a/expect-lava/trusted-firmware.inc
+++ b/expect-lava/trusted-firmware.inc
@@ -13,7 +13,7 @@
         expect_string+=('i;Booting Trusted Firmware')
 
         prompt='Booting BL2'
-        # Catch all 3 possible BL2 loading error messages, namely:
+        # Catch all possible BL2 loading error messages, namely:
         #   "Failure in pre image load handling of BL2"
         #   "Failed to load BL2 firmware."
         #   "Failure in post image load handling of BL2"
@@ -21,5 +21,5 @@
         failures='Fail.*load.*BL2|BL2.*Fail.*load'
         expect_string+=("i;${prompt};;${failures}")
 
-	expect_string+=('i;BL1: Booting BL31')
+        expect_string+=("i;BL1: Booting BL31;;${failures}")
 fi