wl1271: Fix RX path stall

The wl1271_rx function loops through packets in an aggregated buffer. Each
packet in the buffer is handled by a call to wl1271_rx_handle_data, which will
fail if skb memory allocation fails or production mode is enabled. These
failures currently prevent the rx counters to be incremented, thus causing the
rx loop to run forever.

Fix this by ignoring error codes reported wl1271_rx_handle_data function.
This essentially means that frames will be dropped in production mode, which
is the intetion, and frames will be dropped if memory allocation fails, which
is a decent way to recover from that situation.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Tested-by: Tuomas Katila <ext-tuomas.2.katila@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>