bdev: guard bdev_module.h with extern "C"

so the functions declared in this header file are not mangled by
the C++ compiler when building, for instance, a bdev driver, implemented
in C++.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>
Change-Id: I5a5d1abb06d0d3cd5f5d9245bb7c080f3874e83b
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/10745
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot

include/spdk/bdev_module.h

@@ -52,6 +52,10 @@
 #include "spdk/util.h"
 #include "spdk/uuid.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /** Block device module */
 struct spdk_bdev_module {
 	/**
@@ -1290,4 +1294,8 @@ static void __attribute__((constructor)) _spdk_bdev_module_register_##name(void)
 
 #endif /* __SPDK_BDEV_MODULE_ONLY */
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* SPDK_BDEV_MODULE_H */