wifi: rtlwifi: fix possible skb memory leak in `_rtl_pci_rx_interrupt()`.

The function `_rtl_pci_init_one_rxdesc()` can fail even when the new
`skb` is passed because of a DMA mapping error.  If it fails, the `skb`
is not saved in the rx ringbuffer and thus lost.

Compile tested only

Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250616105631.444309-4-fourier.thomas@gmail.com