staging: vt6655: remove redundant assignment of pointer tx_key

staging: vt6655: remove redundant assignment of pointer tx_key

Pointer tx_key is being assigned a value that is never read, it is
being re-assigned a new value later. The assignment is redundant
and can be removed.

Cleans up clan scan build warning:
drivers/staging/vt6655/rxtx.c:1311:3: warning: Value stored
to 'tx_key' is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220307143625.136189-1-colin.i.king@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>