MIPS: generic: Init command line with fw_init_cmdline()

The function bootcmdline_init() in arch/mips/kernel/setup.c will
populate the boot_command_line string using the parameters hardcoded in
the kernel, and those provided in the devicetree file. Then, it would
append the content of the arcs_cmdline variable, which is filled by the
board's plat_mem_setup() function.

The plat_mem_setup() function for the generic MIPS board would just copy
the current boot_command_line to arcs_cmdline, which is nonsense for two
reasons:
- the result will be appended to the boot_command_line anyway, so all it
  does is duplicate every single parameter on the command line;
- the code did not perform at all what it's supposed to, which is to
  retrieve the parameters passed by the bootloader.

Fix this by calling fw_init_cmdline() in plat_mem_setup(), which will
properly initialize arcs_cmdline to the parameters passed by the
bootloader.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/generic/init.c

@@ -106,7 +106,7 @@ void __init plat_mem_setup(void)
 	if (mach && mach->fixup_fdt)
 		fdt = mach->fixup_fdt(fdt, mach_match_data);
 
-	strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE);
+	fw_init_cmdline();
 	__dt_setup_arch((void *)fdt);
 }