mhi: core: Fix memory leak in MHI DE_INIT

During MHI INIT, memory is allocated for firmware and
rddm vector table. This memory is not freed when DE_INIT
is called.

CRs-Fixed: 2053206
Change-Id: I85b2644189915dd25d8ac31190f16799f86cbd12
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>