mmc: block: support no access to boot partitions

Intel Medfield platform blocks access to eMMC boot partitions which
results in switch errors.  Since there is no access, mmcboot0/1
devices should not be created.  Add a host capability to reflect that.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/host/sdhci-pci.c b/drivers/mmc/host/sdhci-pci.c
index 3b30c51..f8a17f9 100644
--- a/drivers/mmc/host/sdhci-pci.c
+++ b/drivers/mmc/host/sdhci-pci.c
@@ -215,6 +215,8 @@
 
 	slot->host->mmc->caps |= MMC_CAP_8_BIT_DATA;
 
+	slot->host->mmc->caps2 = MMC_CAP2_BOOTPART_NOACC;
+
 	return 0;
 }