wcte43x: Build against 2.6.18 and CentOS 5.5

This is to support users who are unable to update to the lastest CentOS 5.x.
There is no change for most users on the latest releases of their distribution.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>

drivers/dahdi/wcte43x-base.c

@@ -51,6 +51,19 @@
 #include "wcxb_spi.h"
 #include "wcxb_flash.h"
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 20)
+#  ifdef RHEL_RELEASE_VERSION
+#    if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(5, 6)
+#      define T43X_HAVE_CANCEL_WORK_SYNC
+#    endif
+#  else
+static inline int delayed_work_pending(struct work_struct *work)
+{
+	return test_bit(0, &work->pending);
+}
+#  endif
+#endif
+
 static const char *TE435_FW_FILENAME = "dahdi-fw-te435.bin";
 static const u32 TE435_VERSION = 0xe0019;
 
@@ -3477,7 +3490,12 @@ static void __devexit t43x_remove_one(struct pci_dev *pdev)
 	wc->vpm = NULL;
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 20)
+#  ifdef T43X_HAVE_CANCEL_WORK_SYNC 
 	cancel_work_sync(&wc->clksrc_work.work);
+#  else
+	cancel_delayed_work(&wc->clksrc_work.work);
+	flush_workqueue(wc->wq);
+#  endif
 #else
 	cancel_delayed_work_sync(&wc->clksrc_work.work);
 #endif