boot-directdisk.bbclass: Fix media generation problems with vmdk

The various populate methods need to accept a path as an argument vs
using hard expanded variables.  In the case of the boot-directdisk
class it uses a different path for HDDDIR but it gets eclipsed by the
the class definition at the point in time ${HDDDIR} gets expanded.

The logical fix is to pass the arguments to the functions as opposed
to using globally expanded variables from the class definitions.

This patch changes 3 things:
1) syslinux_hddimg_populate takes an argument for the destination
2) syslinux_iso_populate takes an argument for the destination
3) populate is changed to boot_direct_populate because there
   was a conflict with it overriding the populate in bootimg.bbclass

[YOCTO #3994]

(From OE-Core rev: 63d164b755b984021f7e3cdba7280918ded6e821)

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/bootimg.bbclass

@@ -86,10 +86,10 @@ build_iso() {
 	populate ${ISODIR}
 
 	if [ "${PCBIOS}" = "1" ]; then
-		syslinux_iso_populate
+		syslinux_iso_populate ${ISODIR}
 	fi
 	if [ "${EFI}" = "1" ]; then
-		grubefi_iso_populate
+		grubefi_iso_populate ${ISODIR}
 		build_fat_img ${EFIIMGDIR} ${ISODIR}/efi.img
 	fi
 
@@ -203,10 +203,10 @@ build_hddimg() {
 		populate ${HDDDIR}
 
 		if [ "${PCBIOS}" = "1" ]; then
-			syslinux_hddimg_populate
+			syslinux_hddimg_populate ${HDDDIR}
 		fi
 		if [ "${EFI}" = "1" ]; then
-			grubefi_hddimg_populate
+			grubefi_hddimg_populate ${HDDDIR}
 		fi
 
 		build_fat_img ${HDDDIR} ${DEPLOY_DIR_IMAGE}/${IMAGE_NAME}.hddimg