[MIPS] Update docs to reflect the latest status of the Alchemy IDE driver.

Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Documentation/mips/AU1xxx_IDE.README

@@ -95,11 +95,13 @@ CONFIG_BLK_DEV_IDEDMA_PCI=y
 CONFIG_IDEDMA_PCI_AUTO=y
 CONFIG_BLK_DEV_IDE_AU1XXX=y
 CONFIG_BLK_DEV_IDE_AU1XXX_MDMA2_DBDMA=y
-CONFIG_BLK_DEV_IDE_AU1XXX_BURSTABLE_ON=y
 CONFIG_BLK_DEV_IDE_AU1XXX_SEQTS_PER_RQ=128
 CONFIG_BLK_DEV_IDEDMA=y
 CONFIG_IDEDMA_AUTO=y
 
+Also define 'IDE_AU1XXX_BURSTMODE' in 'drivers/ide/mips/au1xxx-ide.c' to enable
+the burst support on DBDMA controller.
+
 If the used system need the USB support enable the following kernel configs for
 high IDE to USB throughput.
 
@@ -115,6 +117,8 @@ CONFIG_BLK_DEV_IDE_AU1XXX_SEQTS_PER_RQ=128
 CONFIG_BLK_DEV_IDEDMA=y
 CONFIG_IDEDMA_AUTO=y
 
+Also undefine 'IDE_AU1XXX_BURSTMODE' in 'drivers/ide/mips/au1xxx-ide.c' to
+disable the burst support on DBDMA controller.
 
 ADD NEW HARD DISC TO WHITE OR BLACK LIST
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