ide-dma: fix ide_build_dmatable() for TRM290

Apparently, 'xcount' being 0 does not mean 0 bytes for TRM290; it means 4 bytes,
judging from the code immediately preceding this check.  So, we must never try
to "split" the PRD for TRM290.

This is probably never hit anyway -- with the DMA buffers aligned to at least
512 bytes and ATAPI DMA not being used for non block I/O commands...
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-dma.c

@@ -211,7 +211,7 @@ int ide_build_dmatable (ide_drive_t *drive, struct request *rq)
 				xcount = bcount & 0xffff;
 				if (is_trm290)
 					xcount = ((xcount >> 2) - 1) << 16;
-				if (xcount == 0x0000) {
+				else if (xcount == 0x0000) {
 	/* 
 	 * Most chipsets correctly interpret a length of 0x0000 as 64KB,
 	 * but at least one (e.g. CS5530) misinterprets it as zero (!).