Cast CallVoidMethod's size_t parameters to jint

offset and size variables are passed to set method
of MediaCodec.BufferInfo java class. The corresponding
actual parameters of set method are of int type in java.

These variables are expected to fit in jint as they
indicate the offset and size of data in a media codec
buffer.

The variables are cast to jint, prior to passing to
java method, to avoid problems caused by automatic
type promotion of parameters when passed to a
variadic function, CallVoidMethod.

Change-Id: I39e202306f1b7122448c947f6d275f00251bb33a
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>