staging: android: binder: modify struct binder_write_read to use size_t

This change mirrors the userspace operation where struct binder_write_read
members that specify the buffer size and consumed size are size_t elements.

The patch also fixes the binder_thread_write() and binder_thread_read()
functions prototypes to conform with the definition of binder_write_read.

The changes do not affect existing 32bit ABI.

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>