bionic: Do not use PAGE_SIZE to define PTHREAD_STACK_MIN

There is no need to use PAGE_SIZE to define the value of
PTHREAD_STACK_MIN.

Bug: 312546062
Bug: 313941999
Test: source build/envsetup.sh
      lunch aosp_cf_arm64_phone_pgagnostic-trunk-userdebug
      m
Change-Id: If3c3fe39f50592df58634d1c164e87dcd0aebad0
diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 4feade5..9d99aa1 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -77,12 +77,12 @@
 
 #if defined(__LP64__)
 #if defined(PAGE_SIZE)
-#define PTHREAD_STACK_MIN (4 * PAGE_SIZE)
+#define PTHREAD_STACK_MIN 16384
 #else
 #define PTHREAD_STACK_MIN 65536
 #endif
 #else
-#define PTHREAD_STACK_MIN (2 * PAGE_SIZE)
+#define PTHREAD_STACK_MIN 8192
 #endif
 
 #define PTHREAD_CREATE_DETACHED 1