Fix libc logging implementation.

The file descriptor wasn't getting set, so the writev() call was
silently failing.

There's a parallel implementation over in system/core/liblog, but it's
still using the old approach and didn't have this problem.
diff --git a/libc/bionic/logd_write.c b/libc/bionic/logd_write.c
index 3336428..2c5bf42 100644
--- a/libc/bionic/logd_write.c
+++ b/libc/bionic/logd_write.c
@@ -66,7 +66,7 @@
 
 static pthread_mutex_t log_init_lock = PTHREAD_MUTEX_INITIALIZER;
 
-log_channel_t log_channels[LOG_ID_MAX] = {
+static log_channel_t log_channels[LOG_ID_MAX] = {
     { __write_to_log_null, -1, NULL },
     { __write_to_log_init, -1, "/dev/"LOGGER_LOG_MAIN },
     { __write_to_log_init, -1, "/dev/"LOGGER_LOG_RADIO }
@@ -112,6 +112,7 @@
 
         log_channels[log_id].logger =
             (fd < 0) ? __write_to_log_null : __write_to_log_kernel;
+        log_channels[log_id].fd = fd;
 
         pthread_mutex_unlock(&log_init_lock);