include/pthread: add wait_count to PTHREAD_COND_INITIALIZER

[Zepp-Hanzj]

Summary

PTHREAD_COND_INITIALIZER was missing the initialization of the wait_count field in struct pthread_cond_s, causing a -Wmissing-field-initializers warning when statically initializing condition variables.

Before

struct pthread_cond_s
{
  sem_t sem;
  clockid_t clockid;
  int wait_count;       // ← not initialized
};

#define PTHREAD_COND_INITIALIZER {SEM_INITIALIZER(0), CLOCK_REALTIME }

After

#define PTHREAD_COND_INITIALIZER {SEM_INITIALIZER(0), CLOCK_REALTIME, 0 }

Fixes #19108

Impact

Eliminates -Wmissing-field-initializers warning for PTHREAD_COND_INITIALIZER. No functional change since C guarantees zero-initialization for missing fields in partial initializers, but the explicit initialization is cleaner and silences the warning.

Testing

Verified with grep that all fields of struct pthread_cond_s are now covered by the initializer.

[xiaoxiang781216]

@Zepp-Hanzj already fixed here: #19109

[Zepp-Hanzj]

Got it, thanks for pointing that out! I see that #19109 already addressed this. Closing this PR as duplicate.