.checkpatch.conf: ignore udelay->usleep_range warnings

usleep_range() is a Linux facility, ignore it when udelay()
is encountered.

Signed-off-by: Matt Porter <mporter@ti.com>
diff --git a/.checkpatch.conf b/.checkpatch.conf
index 38386b3..d88af57 100644
--- a/.checkpatch.conf
+++ b/.checkpatch.conf
@@ -15,3 +15,6 @@
 
 # enable more tests
 --strict
+
+# Not Linux, so we don't recommend usleep_range() over udelay()
+--ignore USLEEP_RANGE