Increase iteration count for ordering test

This should make it less likely that the writer finishes before the
reader even starts. It makes the test run longer, but devices have
gotten faster suince this test was written.

Bug: 152218463
Test: Treehugger
Change-Id: I409e59071991095fb17e067760f2a5f29ede0ba2
diff --git a/tests/stdatomic_test.cpp b/tests/stdatomic_test.cpp
index 8a6b267..11d41b4 100644
--- a/tests/stdatomic_test.cpp
+++ b/tests/stdatomic_test.cpp
@@ -181,7 +181,7 @@
 
 // And a rudimentary test of acquire-release memory ordering:
 
-constexpr static uint_least32_t BIG = 10000000ul; // Assumed even below.
+constexpr static uint_least32_t BIG = 30'000'000ul; // Assumed even below.
 
 struct three_atomics {
   atomic_uint_least32_t x;