wic: fix pylint warning redefined-builtin

Renamed variables named as Python builtin functions.

(From OE-Core rev: bed98142e3e47ac2862ccf8fe3e4bdeabfc91172)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/plugins/source/bootimg-pcbios.py

@@ -127,9 +127,9 @@ class BootimgPcbiosPlugin(SourcePlugin):
         'prepares' the partition to be incorporated into the image.
         In this case, prepare content for legacy bios boot partition.
         """
-        def _has_syslinux(dir):
-            if dir:
-                syslinux = "%s/syslinux" % dir
+        def _has_syslinux(dirname):
+            if dirname:
+                syslinux = "%s/syslinux" % dirname
                 if os.path.exists(syslinux):
                     return True
             return False