bcm57xx: correct the MAC status bit positions and name the underrun bit

CFG_CHANGED and SYNC_CHANGED were defined one bit low (0x4 and 0x8
instead of 0x8 and 0x10), so MACSTAT_STICKY never cleared SYNC_CHANGED
and the driver's picture of which attention bits are pending was never
quite the chip's. The rest of the table is filled in while here.

TXSTAT_OFLOW was one of those additions and carried the wrong name:
0x08000000 is the send engine underrunning, the receive overrun is
0x04000000, which the table already calls RXSTAT_OFLOW.

Nothing observed changes from this - the driver only ever tests
LINK_CHANGED, which both versions mask - but a register table that
disagrees with the reference is a trap for the next reader.

Assisted-by: ZCode:deepseek-flash

drivers/ethernet/bcm57xx.inc

@@ -107,10 +107,16 @@ MAC_MODE_TXDMA_EN               = 0x00200000
 MAC_MODE_RXDMA_EN               = 0x00400000
 MAC_MODE_FRMHDR_DMA_EN          = 0x00800000
 
-MACSTAT_CFG_CHANGED             = 0x00000004
-MACSTAT_SYNC_CHANGED            = 0x00000008
+MACSTAT_RX_CFG                  = 0x00000004
+MACSTAT_CFG_CHANGED             = 0x00000008
+MACSTAT_SYNC_CHANGED            = 0x00000010
 MACSTAT_LINK_CHANGED            = 0x00001000
 MACSTAT_MI_COMPLETE             = 0x00400000
+MACSTAT_MI_INTERRUPT            = 0x00800000
+MACSTAT_AUTOPOLL_ERROR          = 0x01000000
+MACSTAT_ODI_ERROR               = 0x02000000
+MACSTAT_RXSTAT_OFLOW            = 0x04000000      ; receive overrun
+MACSTAT_TXSTAT_UNDERRUN         = 0x08000000      ; send underrun; 0x04000000 is the RX one
 MACSTAT_STICKY                  = MACSTAT_LINK_CHANGED or MACSTAT_SYNC_CHANGED \
                                   or MACSTAT_CFG_CHANGED or MACSTAT_MI_COMPLETE
 EVTENB_LINK_CHANGED             = 0x00001000