msm: ADSPRPC: Fix leak that happens while the list gets empty

When the list that holds the open file handles gets empty, the
node does not get freed causing a leak.

Change-Id: I611387abd27033d4ded63b3bf271162c5d95653d
Acked-by: Chenna Kesava Raju <chennak@qti.qualcomm.com>
Signed-off-by: Sathish Ambley <sathishambley@codeaurora.org>