test: Drop the blank line before test macros

Most tests don't have this. It helps to keep the test declaration
clearly associated with the function it relates to, rather than the next
one in the file. Remove the extra blank line and mention this in the
docs.

Signed-off-by: Simon Glass <sjg@chromium.org>

test/cmd/exit.c

@@ -121,7 +121,6 @@ static int cmd_exit_test(struct unit_test_state *uts)
 
 	return 0;
 }
-
 EXIT_TEST(cmd_exit_test, UTF_CONSOLE_REC);
 
 int do_ut_exit(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])