mfd: Add TPS659038 documentation under Palmas

Add TPS659038 Device Tree documentation.
Acked-by: NSamuel Ortiz <sameo@linux.intel.com>
Signed-off-by: NJ Keerthy <j-keerthy@ti.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

Documentation/devicetree/bindings/mfd/palmas.txt

@@ -5,6 +5,7 @@ twl6035 (palmas)
 twl6037 (palmas)
 tps65913 (palmas)
 tps65914 (palmas)
+tps659038
 
 Required properties:
 - compatible : Should be from the list
@@ -14,6 +15,7 @@ Required properties:
   ti,tps65913
   ti,tps65914
   ti,tps80036
+  ti,tps659038
 and also the generic series names
   ti,palmas
 - interrupt-controller : palmas has its own internal IRQs