download/mrc: handle exit status within subshell

the previous code merely exited from the subshell,
but the intended behaviour is for the entire script
to halt execution, and exit with non-zero status.

this patch fixes that bug.

resources/scripts/download/mrc

@@ -43,8 +43,11 @@ _mrc_complete="mrc/haswell/mrc.bin"
 cbdir="coreboot/default"
 cbfstool="${cbdir}/util/cbfstool/cbfstool"
 
+sname=""
+
 main()
 {
+	sname=${0}
 	printf "Downloading Intel MRC blobs\n"
 
 	check_existing && exit 0
@@ -90,9 +93,7 @@ fetch_mrc()
 		download_image ${_url2} ${_file} ${_sha1sum}
 	fi
 	if [ ! -f $_file ]; then
-		printf "%s not downloaded / verification failed. Exiting.\n" \
-				${_file}
-		exit 1
+		fail "%{_file} not downloaded / verification failed."
 	fi
 
 	extract_partition ROOT-A ${_file} root-a.ext2
@@ -173,4 +174,11 @@ extract_coreboot()
 	rm -r "${_unpacked}"
 }
 
+fail()
+{
+	printf "%s: ERROR: %s\n"
+			${sname} ${1}
+	exit 1
+}
+
 main $@