driver: watchdog: add sp805 watchdog support

sp805 is watchdog on some NXP layerscape SoCs, adding
it's driver. Configs CONFIG_WDT_SP805, CONFIG_WDT, CONFIG_CMD_WDT
needs to be enabled to use it.

Signed-off-by: Zhao Qiang <qiang.zhao@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index c41bc89..3662579 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -519,6 +519,7 @@
 M:	Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
 S:	Maintained
 T:	git git://git.denx.de/u-boot-fsl-qoriq.git
+F:	drivers/watchdog/sp805_wdt.c
 
 I2C
 M:	Heiko Schocher <hs@denx.de>