msm: vidc: refine decode batching logic

1. is_batching_allowed api is not considering platform
check(core->resources.decode_batching).
2. increase both input & output buffers count if
current session supports batching.

Change-Id: Iabe7479b4664a78b637ee981d67c604f7d0d5d56
Signed-off-by: Govindaraj Rajagopal <grajagop@codeaurora.org>