vfs: zero-initialize struct stat in *_stat and *_fstat handlers

...otherwise some fields will contain garbage values.
This wasn't noticed until HAVE_BLKSIZE got enabled in newlib builds.

components/fatfs/vfs/vfs_fat.c

@@ -552,6 +552,7 @@ static int vfs_fat_fstat(void* ctx, int fd, struct stat * st)
 {
     vfs_fat_ctx_t* fat_ctx = (vfs_fat_ctx_t*) ctx;
     FIL* file = &fat_ctx->files[fd];
+    memset(st, 0, sizeof(*st));
     st->st_size = f_size(file);
     st->st_mode = S_IRWXU | S_IRWXG | S_IRWXO | S_IFREG;
     st->st_mtime = 0;

components/spiffs/esp_spiffs.c

@@ -536,6 +536,7 @@ static int vfs_spiffs_fstat(void* ctx, int fd, struct stat * st)
         SPIFFS_clearerr(efs->fs);
         return -1;
     }
+    memset(st, 0, sizeof(*st));
     st->st_size = s.size;
     st->st_mode = S_IRWXU | S_IRWXG | S_IRWXO | S_IFREG;
     st->st_mtime = vfs_spiffs_get_mtime(&s);
@@ -558,7 +559,7 @@ static int vfs_spiffs_stat(void* ctx, const char * path, struct stat * st)
         SPIFFS_clearerr(efs->fs);
         return -1;
     }
-
+    memset(st, 0, sizeof(*st));
     st->st_size = s.size;
     st->st_mode = S_IRWXU | S_IRWXG | S_IRWXO;
     st->st_mode |= (s.type == SPIFFS_TYPE_DIR)?S_IFDIR:S_IFREG;

components/tinyusb/additions/src/vfs_tinyusb.c

@@ -207,6 +207,7 @@ static ssize_t tusb_read(int fd, void *data, size_t size)
 static int tusb_fstat(int fd, struct stat *st)
 {
     FD_CHECK(fd, -1);
+    memset(st, 0, sizeof(*st));
     st->st_mode = S_IFCHR;
     return 0;
 }

components/vfs/vfs_cdcacm.c

@@ -96,6 +96,7 @@ static int cdcacm_open(const char *path, int flags, int mode)
 static int cdcacm_fstat(int fd, struct stat *st)
 {
     assert(fd == 0);
+    memset(st, 0, sizeof(*st));
     st->st_mode = S_IFCHR;
     return 0;
 }

components/vfs/vfs_uart.c

@@ -291,7 +291,7 @@ static ssize_t uart_read(int fd, void* data, size_t size)
 static int uart_fstat(int fd, struct stat * st)
 {
     assert(fd >=0 && fd < 3);
-    st->st_blksize = BUFSIZ;
+    memset(st, 0, sizeof(*st));
     st->st_mode = S_IFCHR;
     return 0;
 }