[POWERPC] Remove cmd_line from head*.S

It is just a C char array, so declare it thusly.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/setup-common.c

@@ -76,6 +76,8 @@ EXPORT_SYMBOL(machine_id);
 
 unsigned long klimit = (unsigned long) _end;
 
+char cmd_line[COMMAND_LINE_SIZE];
+
 /*
  * This still seems to be needed... -- paulus
  */