staging: r8188eu: remove empty function rtw_get_encrypt_decrypt_from_registrypriv

The definition of function rtw_get_encrypt_decrypt_from_registrypriv is
empty. Remove it.

Signed-off-by: Abdun Nihaal <abdun.nihaal@gmail.com>
Link: https://lore.kernel.org/r/3d84df54e73b49464d2a0732b44acdb71687b3b1.1644422181.git.abdun.nihaal@gmail.com


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