Don't use size_t for variables that store uint32_t value

The local variables width, height, displayWidth and
displayHeight are set to the corresponding members
of VideoFrame class. As the members of VideoFrame are
uint32_t, the local variables have been changed to
uint32_t.

As these local variables are passed to a java method,
the change of size_t to uint32_t ensures that the size
of the actual parameter (i.e uint32_t) is now same as
the size of the formal parameter (i.e. jint) for all
platforms.

Change-Id: Icd14de0142bfd4e6ba52a3e6aff3d80b323a0de4
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>