bdev: spdk_bdev_module_init_done with async init

spdk_bdev_module_init() must only be called if the module sets
async_init to true. This patch fixes the doc string to match the
implementation and adds an assert() to catch API usage errors early.

Change-Id: I677345de028c8f7597ecf81ff9b9b855867bbf01
Signed-off-by: Mike Gerdts <mgerdts@nvidia.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/16133
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Mellanox Build Bot
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <smatsumoto@nvidia.com>

include/spdk/bdev_module.h

@@ -951,8 +951,8 @@ void spdk_bdev_module_examine_done(struct spdk_bdev_module *module);
 /**
  * Indicate to the bdev layer that the module is done initializing.
  *
- * To be called once during module_init or asynchronously after
- * an asynchronous operation required for module initialization is completed.
+ * To be called once after an asynchronous operation required for module initialization is
+ * completed. If module->async_init is false, the module must not call this function.
  *
  * \param module Pointer to the module completing the initialization.
  */

lib/bdev/bdev.c

@@ -1583,6 +1583,7 @@ bdev_module_action_done(struct spdk_bdev_module *module)
 void
 spdk_bdev_module_init_done(struct spdk_bdev_module *module)
 {
+	assert(module->async_init);
 	bdev_module_action_done(module);
 }