AArch64: Use long for pointers in graphics/Camera

For storing pointers, long is used in
android/graphics/Camera class, 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: Ic05ebf2051a225a1638a43f476bab6176c0b5c38
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>