HELLO: review unused symbols

Remove unused functions:
- hello_register_commands

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>

src/hello.h

@@ -20,12 +20,8 @@
 #ifndef OPENOCD_HELLO_H
 #define OPENOCD_HELLO_H
 
-struct command_context;
 struct command_registration;
 
-/// Register the hello commands in the specified command_context
-int hello_register_commands(struct command_context *cmd_ctx);
-
 /**
  * Export the registration for the hello command group, so it can be
  * embedded in example drivers.