trusty: storageproxyd: Fix rebase of UFS support

The UFS support got rebased on top of the RPMB socket support
improperly. As a result, RPMB socket support was broken due to an
unconditional rmpb_fd = rc which would set the rpmb_fd to be connect()'s
error code in the case of an RPMB socket.

Bug: 146903427
Test: Boot Trusty+Android with the rpmb_dev mock, check for liveness
Change-Id: Ib1220dc49392f1a10369eed7716e44680bd83a66