wic/qemuarm64: enabled kernel arguments with u-boot

Kernel commandline arguments passed via runqemu don't
configure the kernel when booting with u-boot, as it finds
configuration in extlinux/extlinux.conf instead, which is
generated by wic.

A custom extlinux.conf file is now passed to wic with the
intended arguments, so that the kernel now configures
as directed.

Change-Id: Icbbcab47fe5cf70e4d8d39c7145371f1d6cd8db7
Signed-off-by: Brett Warren <brett.warren@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/wic/qemuarm64.cfg

@@ -0,0 +1,4 @@
+default Yocto
+label Yocto
+    kernel /Image
+append root=/dev/vda2 rw console=ttyS0 mem=1024M ip=192.168.7.2::192.168.7.1:255.255.255.0 console=ttyAMA0

meta-arm/wic/qemuarm64.wks

@@ -1,4 +1,4 @@
-bootloader --ptable gpt
+bootloader --ptable gpt --configfile="qemuarm64.cfg"
 
 part /boot --ondisk=vda --align 64 --size=100M --active --source bootimg-partition --fstype=ext4 --label boot --sourceparams="loader=u-boot"
 part /     --ondisk=vda                                 --source rootfs            --fstype=ext4 --label root