usb: Add utility for D-Bus

Putting all D-Bus related operation to the utils file.

Tested: Call the set/getProperty functions locally and successfully
set/get the corresponding attribute value.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I0e0c33fd6ec5db3a47babaf417b0c708709e580b
3 files changed