kdb: Const qualifier for kdb_getstr's prompt argument

All current callers of kdb_getstr() can pass constant pointers via the
prompt argument. This patch adds a const qualification to make explicit
the fact that this is safe.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

kernel/debug/kdb/kdb_io.c

@@ -439,7 +439,7 @@ static char *kdb_read(char *buffer, size_t bufsize)
  *	substituted for %d, %x or %o in the prompt.
  */
 
-char *kdb_getstr(char *buffer, size_t bufsize, char *prompt)
+char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt)
 {
 	if (prompt && kdb_prompt_str != prompt)
 		strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);

kernel/debug/kdb/kdb_private.h

@@ -211,7 +211,7 @@ extern void kdb_ps1(const struct task_struct *p);
 extern void kdb_print_nameval(const char *name, unsigned long val);
 extern void kdb_send_sig_info(struct task_struct *p, struct siginfo *info);
 extern void kdb_meminfo_proc_show(void);
-extern char *kdb_getstr(char *, size_t, char *);
+extern char *kdb_getstr(char *, size_t, const char *);
 extern void kdb_gdb_state_pass(char *buf);
 
 /* Defines for kdb_symbol_print */