AArch64: Use long for pointers in audio effect classes

For storing pointers, long is used in AudioEffect
and Visualizer classes, as native pointers can be 64-bit.

In addition, some minor changes have been done
to conform with standard JNI practice (e.g. use
of jint instead of int in JNI function prototypes)

Change-Id: Ief49bbe5baef663e268c7f6d70ac33a4df45621c
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>
Signed-off-by: Kévin PETIT <kevin.petit@arm.com>