MAINTAINERS: Add fragment for Xilinx watchdog driver

Added entry for Xilinx xps-timebase watchdog driver.

Signed-off-by: Srinivas Neeli <srinivas.neeli@amd.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230420104231.2243079-2-srinivas.neeli@amd.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>