MIPS: TXx9: Improve handling of built-in and command-line args

* Make prom_init_cmdline() static and be called from prom_init.
* Append built-in args if the first character was '+'.
* Drop command-line args if the first character of built-in was '-'.
* Enclose args include spaces by quotes.
* TX4938_NAND_BOOT is no longer needed.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/txx9/rbtx4927/prom.c

@@ -36,7 +36,6 @@
 
 void __init rbtx4927_prom_init(void)
 {
-	prom_init_cmdline();
 	add_memory_region(0, tx4927_get_mem_size(), BOOT_MEM_RAM);
 	txx9_sio_putchar_init(TX4927_SIO_REG(0) & 0xfffffffffULL);
 }