iomx: simplify param/config size getter.
iomx: simplify param/config size getter.

"OMX_U32 nSize" is the first element of each OMX param/config struct.

Signed-off-by: Martin Storsjö <54669547a225ff20cba8b75a4adca540eef25858@martin.st>
(cherry picked from commit 2ef0f162c45d491e7c60d3f0caa9ad4df38297c5)
Signed-off-by: Jean-Baptiste Kempf <7b85a41a628204b76aba4326273a3ccc74bd009a@videolan.org>

jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2