add Marvell 88W8688 support to libertas_sdio

This chip is for example used in the GuruPlug.
This patch avoids the following error:
libertas_sdio: failed to load firmware
libertas_sdio: probe of mmc0:0001:1 failed with error -5

The fix is based on code in:
drivers/net/wireless/libertas_uap/uap_sdio_mmc.c

This file can for example be found on the following links:
http://www.xilka.com/sheeva/2.6/2.6.36/2.6.36.2/source/0002-Driver-for-Marvell-Libertas-8688-SDIO-micro-AP-suppo-2.6.35.patch
http://www.downloadsnewit.co.uk/kernel-v3.0.7/

I followed the following wiki to setup a working WiFi client mode
connection on the GuruPlug:
http://wiki.debian.org/libertasSigned-off-by: Harro Haan <hrhaan@gmail.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/if_sdio.c

@@ -588,17 +588,38 @@ static int if_sdio_prog_real(struct if_sdio_card *card,
 	size = fw->size;
 
 	while (size) {
+		timeout = jiffies + HZ;
+		while (1) {
 			ret = if_sdio_wait_status(card, FW_DL_READY_STATUS);
 			if (ret)
 				goto release;
 
-		req_size = sdio_readb(card->func, IF_SDIO_RD_BASE, &ret);
+			req_size = sdio_readb(card->func, IF_SDIO_RD_BASE,
+					&ret);
 			if (ret)
 				goto release;
 
-		req_size |= sdio_readb(card->func, IF_SDIO_RD_BASE + 1, &ret) << 8;
+			req_size |= sdio_readb(card->func, IF_SDIO_RD_BASE + 1,
+					&ret) << 8;
 			if (ret)
 				goto release;
+
+			/*
+			 * For SD8688 wait until the length is not 0, 1 or 2
+			 * before downloading the first FW block,
+			 * since BOOT code writes the register to indicate the
+			 * helper/FW download winner,
+			 * the value could be 1 or 2 (Func1 or Func2).
+			 */
+			if ((size != fw->size) || (req_size > 2))
+				break;
+			if (time_after(jiffies, timeout)) {
+				ret = -ETIMEDOUT;
+				goto release;
+			}
+			mdelay(1);
+		}
+
 /*
 		lbs_deb_sdio("firmware wants %d bytes\n", (int)req_size);
 */