u-boot: remove legacy staging

A recent commit seems to have introduced a legacy staging function, remove it

Signed-off-by: Joshua Lock <josh@linux.intel.com>

meta/packages/uboot/u-boot.inc

@@ -34,7 +34,7 @@ do_deploy () {
 do_deploy[dirs] = "${S}"
 addtask deploy before do_build after do_compile
 
-do_stage() {
-	install -d ${STAGING_BINDIR_NATIVE}
-	install -m 755 tools/mkimage ${STAGING_BINDIR_NATIVE}/
+do_install() {
+	install -d ${D}${bindir}
+	install -m 755 tools/mkimage ${D}${bindir}/
 }