power: Add type casting to support architecture-independent API porting.

power: Add type casting to support architecture-independent API porting.

At first, in the 32bit architecture, power state enum value is treated as 4 byte.
Thus, when dealing with enum value, the type should be converted to unsigned int or int.
Especially, this is necessary for C# API porting in the 32bit architecture to avoid abnormal operation.
However, when the device_power_change_state uses dbus call, it treats enum value as uint64_t in the g_variant type.
To make correct type conversion in g_variant, uint64_t type conversion is needed also.

Change-Id: I2e9ef7a715ca5beb13f358e183f5b054cff86ce1
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>