staging: r8188eu: remove unused local variable

Remove unused local variable padapter from rtl8188eu_init_recvbuf().
Function is not using this variable.

Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
Link: https://lore.kernel.org/r/YXWnd5X9+p0X+1EB@Sauravs-MacBook-Air.local
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>