bgmac: increase rx ring size from 511 to 512

Limiting it to 511 looks like a failed attempt at leaving one descriptor
empty to allow the hardware to stop processing a buffer that has not
been prepared yet. However, this doesn't work because this affects the
total ring size as well

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bgmac.h

@@ -356,7 +356,7 @@
 #define BGMAC_MAX_RX_RINGS			1
 
 #define BGMAC_TX_RING_SLOTS			128
-#define BGMAC_RX_RING_SLOTS			512 - 1		/* Why -1? Well, Broadcom does that... */
+#define BGMAC_RX_RING_SLOTS			512
 
 #define BGMAC_RX_HEADER_LEN			28		/* Last 24 bytes are unused. Well... */
 #define BGMAC_RX_FRAME_OFFSET			30		/* There are 2 unused bytes between header and real data */