binder: relocate binder_alloc_clear_buf()

Move this function up along with binder_alloc_get_page() so that their
prototypes aren't necessary.

No functional change in this patch.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20231201172212.1813387-16-cmllamas@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>