staging: android: binder: fix BINDER_SET_MAX_THREADS declaration

This change will fix the BINDER_SET_MAX_THREADS ioctl to use __u32
instead of size_t for setting the max threads. Thus using the same
handler for 32 and 64bit kernels.

This value is stored internally in struct binder_proc and set to 15
on open_binder() in the libbinder API(thus no need for a 64bit size_t
on 64bit platforms).

The change does not affect existing 32bit ABI.

Change-Id: Ibdfe10a70d475a91c247dc36e9cfd74a259d50e4
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>
Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>