LoongArch: Fix CMDLINE_EXTEND and CMDLINE_BOOTLOADER handling

On FDT systems these command line processing are already taken care of
by early_init_dt_scan_chosen(). Add similar handling to the ACPI (non-
FDT) code path to allow these config options to work for ACPI (non-FDT)
systems too.
Signed-off-by: Zhihong Dong <donmor3000@hotmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kernel/setup.c

@@ -332,9 +332,25 @@ static void __init bootcmdline_init(char **cmdline_p)
 			strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
 
 		strlcat(boot_command_line, init_command_line, COMMAND_LINE_SIZE);
+		goto out;
 	}
 #endif
 
+	/*
+	 * Append built-in command line to the bootloader command line if
+	 * CONFIG_CMDLINE_EXTEND is enabled.
+	 */
+	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && CONFIG_CMDLINE[0]) {
+		strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+		strlcat(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+	}
+
+	/*
+	 * Use built-in command line if the bootloader command line is empty.
+	 */
+	if (IS_ENABLED(CONFIG_CMDLINE_BOOTLOADER) && !boot_command_line[0])
+		strscpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+
 out:
 	*cmdline_p = boot_command_line;
 }