ARC: [cmdline] Don't overwrite u-boot provided bootargs

The existing code was wrong on several counts:

* uboot provided bootargs were copied into @boot_command_line, only to
  be over-written by setup_machine_fdt(), effectively lost

* @cmdline_p returned by setup_arch() to start_kernel() didn't include
  the DT /bootargs
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/setup.c

@@ -318,18 +318,20 @@ void __cpuinit setup_processor(void)
 
 void __init setup_arch(char **cmdline_p)
 {
+	/* This also populates @boot_command_line from /bootargs */
+	machine_desc = setup_machine_fdt(__dtb_start);
+	if (!machine_desc)
+		panic("Embedded DT invalid\n");
+
+	/* Append any u-boot provided cmdline */
 #ifdef CONFIG_CMDLINE_UBOOT
-	/* Make sure that a whitespace is inserted before */
-	strlcat(command_line, " ", sizeof(command_line));
+	/* Add a whitespace seperator between the 2 cmdlines */
+	strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+	strlcat(boot_command_line, command_line, COMMAND_LINE_SIZE);
 #endif
 
 	/* Save unparsed command line copy for /proc/cmdline */
-	strlcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
-	*cmdline_p = command_line;
-
-	machine_desc = setup_machine_fdt(__dtb_start);
-	if (!machine_desc)
-		panic("Embedded DT invalid\n");
+	*cmdline_p = boot_command_line;
 
 	/* To force early parsing of things like mem=xxx */
 	parse_early_param();