gdbstub: Replace strcpy() by strscpy()

The strcpy() function is being deprecated. Replace it by the safer
strscpy() and fix the following Coverity warning:

"You might overrun the 1024-character fixed-size string remcom_in_buffer
by copying cmd without checking the length."

Addresses-Coverity-ID: 138999 ("Copy into fixed size buffer")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

kernel/debug/gdbstub.c

@@ -1095,10 +1095,10 @@ int gdbstub_state(struct kgdb_state *ks, char *cmd)
 		return error;
 	case 's':
 	case 'c':
-		strcpy(remcom_in_buffer, cmd);
+		strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
 		return 0;
 	case '$':
-		strcpy(remcom_in_buffer, cmd);
+		strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
 		gdbstub_use_prev_in_buf = strlen(remcom_in_buffer);
 		gdbstub_prev_in_buf_pos = 0;
 		return 0;