staging: android: ion: Validate hyp assign number of elements

Ensure that when we are calling hyp_assign_table that the source and
destination vmid lists each contain at least one vmid since that is
required by hyp_assign.

Change-Id: Ib9d95b3b8333723e40a0027dc54e770eb792b30f
Signed-off-by: Liam Mark <lmark@codeaurora.org>