staging: android: binder.c: binder_ioctl() cleanup

binder_ioctl() is quite huge and checkpatch dirty - mostly because of
the amount of code for the BINDER_WRITE_READ and BINDER_SET_CONTEXT_MGR.
Moved that code into the new binder_ioctl_write_read() and
binder_ioctl_set_ctx_mgr()

Signed-off-by: Tair Rzayev <tair.rzayev@gmail.com>
Cc: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>