pdbg: needs host dtc

Fixes:
http://autobuild.buildroot.net/results/722/722e043ef7503abe5fd6517c82b0f12627f4b0f4/
http://autobuild.buildroot.net/results/891/8918121581f9834fef55169599766a9134600e89/
http://autobuild.buildroot.net/results/475/475106ec793e16bf8c250d3a69e853537e3e0def/

Cc: Joel Stanley <joel@jms.id.au>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/pdbg/pdbg.mk

@@ -9,6 +9,7 @@ PDBG_SITE = $(call github,open-power,pdbg,$(PDBG_VERSION))
 PDBG_LICENSE = Apache-2.0
 PDBG_LICENSE_FILES = COPYING
 PDBG_AUTORECONF = YES
+PDBG_DEPENDENCIES = host-dtc
 
 PDBG_MAKE_OPTS = "GIT_SHA1=\"$(PDBG_VERSION)\""