staging: vt6655: Fix warnings if CONFIG_PM is not defined

If staging:vt6655 is built without CONFIG_DM being defined, there are large
numbers of warnings of the following form due to use of #if instead of #ifdef:

In file included from drivers/staging/vt6655/upc.h:32,
                 from drivers/staging/vt6655/mac.h:39,
                 from drivers/staging/vt6655/wroute.c:34:
drivers/staging/vt6655/device.h:399:5: warning: "CONFIG_PM" is not defined

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>