[PARISC] OS_ID_LINUX == 0x0006

We were assigned an OS_ID of 0x0006. Consistently use OS_ID_LINUX
instead of using the magic number. Also update the OS_ID_ defines in
asm/pdc.h to reflect this.

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

arch/parisc/kernel/setup.c

@@ -303,7 +303,7 @@ extern void eisa_init(void);
 
 static int __init parisc_init(void)
 {
-	u32 osid = (0x0006 << 16);
+	u32 osid = (OS_ID_LINUX << 16);
 
 	parisc_proc_mkdir();
 	parisc_init_resources();