tegra-minimal-init: dont assume boot device /dev/mmcblk0p1

Dont assume boot device is /dev/mmcblk0p1, there is a variable
TNSPEC_BOOTDEV in machine conf is for that purpose, use that.

Signed-off-by: Ming Liu <liu.ming50@gmail.com>

recipes-core/initrdscripts/tegra-minimal-init/platform-preboot.sh

@@ -37,6 +37,6 @@ if [ -z "$rootdev" ]; then
     if [ -n "$mayberoot" ]; then
 	rootdev="$mayberoot"
     else
-	rootdev="/dev/mmcblk0p1"
+	rootdev="/dev/@@TNSPEC_BOOTDEV@@"
     fi
 fi

recipes-core/initrdscripts/tegra-minimal-init_1.0.bb

@@ -9,6 +9,8 @@ SRC_URI = "\
 
 COMPATIBLE_MACHINE = "(tegra)"
 
+PACKAGE_ARCH = "${MACHINE_ARCH}"
+
 S = "${WORKDIR}"
 
 do_install() {
@@ -19,6 +21,7 @@ do_install() {
     mknod -m 622 ${D}/dev/console c 5 1
     install -d ${D}${sysconfdir}
     install -m 0644 ${WORKDIR}/platform-preboot.sh ${D}${sysconfdir}/platform-preboot
+    sed -i -e "s#@@TNSPEC_BOOTDEV@@#${TNSPEC_BOOTDEV}#g" ${D}${sysconfdir}/platform-preboot
 }
 
 RDEPENDS:${PN} = "util-linux-blkid"