Add security patch level check in DSULoader

There's an enforced check enabled in locked devices. It requires
the installed DSU to have a security patch level equal or higher
than the device. This CL adds the SPL check in the DSULoader.

Bug: 151790609
Test: Developer Settings -> DSULoader
Change-Id: Ifef4175e846f58d8033cf161d7fec8481dc0532b
1 file changed