msm: vidc: Fix validate_pkt_size macro definition

Convert validate_pkt_size macro to an inline function
as this macro definition always returns true.

Change-Id: I9e7eadfe82c041721565c880eca3a46e4e3e98d9
Signed-off-by: Priyanka Gujjula <pgujjula@codeaurora.org>