Decoder: Corrected variable datatypes in ih264d_get_implicit_weights.

The difference between two 32 signed numbers was getting assigned
to 16 bits, leading to a divide by zero arithmetic execption.
Modified variable names to match their datatypes.

Bug: 65122447

Change-Id: I45ade1945f10b4d7660bd09fb564e60fd29d40dc
1 file changed