mac80211: b43: Increase number of RX DMA slots

Bastian Bittorf reported that some of the silent freezes on a Linksys WRT54G
were due to overflow of the RX DMA ring buffer, which was created with 64
slots. That finding reminded me that I was seeing similar crashed on a netbook,
which also has a relatively slow processor. After increasing the number of
slots to 128, runs on the netbook that previously failed now worked; however,
I found that 109 slots had been used in one test. For that reason, the number
of slots is being increased to 256.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>

SVN-Revision: 35671

package/mac80211/patches/840-43-increase_number_of_rx_dma_slots.patch

+--- a/drivers/net/wireless/b43/dma.h
++++ b/drivers/net/wireless/b43/dma.h
+@@ -169,7 +169,7 @@ struct b43_dmadesc_generic {
+ 
+ /* DMA engine tuning knobs */
+ #define B43_TXRING_SLOTS		256
+-#define B43_RXRING_SLOTS		64
++#define B43_RXRING_SLOTS		256
+ #define B43_DMA0_RX_FW598_BUFSIZE	(B43_DMA0_RX_FW598_FO + IEEE80211_MAX_FRAME_LEN)
+ #define B43_DMA0_RX_FW351_BUFSIZE	(B43_DMA0_RX_FW351_FO + IEEE80211_MAX_FRAME_LEN)
+