[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>
diff --git a/drivers/parisc/pdc_stable.c b/drivers/parisc/pdc_stable.c
index a109421..97b3458 100644
--- a/drivers/parisc/pdc_stable.c
+++ b/drivers/parisc/pdc_stable.c
@@ -884,7 +884,7 @@
 	if (!entry || !buf || !count)
 		return -EINVAL;
 
-	if (unlikely(pdcs_osid != 0x0006))
+	if (unlikely(pdcs_osid != OS_ID_LINUX))
 		return -EPERM;
 
 	if (count > 16)
@@ -926,7 +926,7 @@
 	if (unlikely(pdcs_size <= 224))
 		return -ENOSYS;
 
-	if (unlikely(pdcs_osid != 0x0006))
+	if (unlikely(pdcs_osid != OS_ID_LINUX))
 		return -EPERM;
 
 	size = pdcs_size - 224;