staging: rtl8192e: Remove function rtl92e_update_rx_pkt_timestamp()

staging: rtl8192e: Remove function rtl92e_update_rx_pkt_timestamp()

mac_time and last_rx_desc_tsf are only used in
rtl92e_update_rx_pkt_timestamp(). Depending on a condition one is equal
to the other or vice versa. But since those are not used anywhere else
the function rtl92e_update_rx_pkt_timestamp() is just dead code.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/89a21fa17b32d66e07514bfad5b604d5d4835e25.1700860759.git.philipp.g.hortmann@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>