ppc32: Don't make cmd_line be an emptry string

As noted by Olaf Hering, CONFIG_CMDLINE didn't work on PMacs
as we made cmd_line be an empty string and then looked for the
cmdline in odd places.
Signed-off-by: Tom Rini <trini@kernel.crashing.org>

arch/ppc/kernel/setup.c

@@ -418,7 +418,6 @@ platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
 	 * are used for initrd_start and initrd_size,
 	 * otherwise they contain 0xdeadbeef.
 	 */
-	cmd_line[0] = 0;
 	if (r3 >= 0x4000 && r3 < 0x800000 && r4 == 0) {
 		strlcpy(cmd_line, (char *)r3 + KERNELBASE,
 			sizeof(cmd_line));