meta-ibm: genesis3: make required kernel dts change

This system still just utilizes the evb dts but it does need to be
updated for the latest 6.5 changes that moved these to an aspeed
sub-directory.

Tested:
- Confirmed genesis3 builds again

Change-Id: I0bea023e2f1e58b4b52ea22eda4de063febc5a39
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
diff --git a/meta-ibm/meta-genesis3/conf/machine/genesis3.conf b/meta-ibm/meta-genesis3/conf/machine/genesis3.conf
index e1d3eb7..3c03fbc 100644
--- a/meta-ibm/meta-genesis3/conf/machine/genesis3.conf
+++ b/meta-ibm/meta-genesis3/conf/machine/genesis3.conf
@@ -1,5 +1,5 @@
 KMACHINE = "aspeed"
-KERNEL_DEVICETREE = "${KMACHINE}-ast2500-evb.dtb"
+KERNEL_DEVICETREE = "aspeed/${KMACHINE}-ast2500-evb.dtb"
 
 PREFERRED_PROVIDER_virtual/bootloader = "u-boot-aspeed"
 PREFERRED_PROVIDER_u-boot = "u-boot-aspeed"