disk: Use Makefile to omit partition drivers

At present these files have an #ifdef covering the whole file. Move the
condition to the Makefile instead.

Add BLK to the condition since future patches will adjust things so that
HAVE_BLOCK_DEVICE is only for SPL, but the partition drivers are needed
in U-Boot proper too.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/Makefile b/drivers/Makefile
index eba9940..f2154e1 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -60,6 +60,7 @@
 obj-$(CONFIG_OMAP_USB_PHY) += usb/phy/
 obj-$(CONFIG_SPL_SATA) += ata/ scsi/
 obj-$(CONFIG_HAVE_BLOCK_DEVICE) += block/
+obj-$(CONFIG_SPL_BLK) += block/
 obj-$(CONFIG_SPL_THERMAL) += thermal/
 
 endif