watchdog: pcwd_usb: Fix attempting to access uninitialized memory

watchdog: pcwd_usb: Fix attempting to access uninitialized memory

The stack variable msb and lsb may be used uninitialized in function
usb_pcwd_get_temperature and usb_pcwd_get_timeleft when usb card no response.

The build waring is:
drivers/watchdog/pcwd_usb.c:336:22: error: ‘lsb’ is used uninitialized in this function [-Werror=uninitialized]
  *temperature = (lsb * 9 / 5) + 32;
                  ~~~~^~~
drivers/watchdog/pcwd_usb.c:328:21: note: ‘lsb’ was declared here
  unsigned char msb, lsb;
                     ^~~
cc1: all warnings being treated as errors
scripts/Makefile.build:250: recipe for target 'drivers/watchdog/pcwd_usb.o' failed
make[3]: *** [drivers/watchdog/pcwd_usb.o] Error 1

Fixes: b7e04f8c61a4 ("mv watchdog tree under drivers")
Signed-off-by: Li Hua <hucool.lihua@huawei.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20221116020706.70847-1-hucool.lihua@huawei.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>