u-boot-aspeed: improve env handling

This fixes some build errors we faced due to add new ast2500-based
platform.
* Allow to redefine input env file.
* Backport providing "u-boot-default-env" from u-boot.inc
* PROVIDES += "u-boot-fw-utils" is not enough, add also RPROVIDES

Last two changes allows to exclude from build modern libubootenv which
somewhy doesn't work for us.

Signed-off-by: Andrei Kartashev <a.kartashev@yadro.com>
Change-Id: I33f152c572f6c0b4d8b608375b252290efacd1ea
diff --git a/meta-aspeed/recipes-bsp/u-boot/u-boot-aspeed.inc b/meta-aspeed/recipes-bsp/u-boot/u-boot-aspeed.inc
index 19de5d2..3028a9e 100644
--- a/meta-aspeed/recipes-bsp/u-boot/u-boot-aspeed.inc
+++ b/meta-aspeed/recipes-bsp/u-boot/u-boot-aspeed.inc
@@ -182,7 +182,11 @@
 
 }
 
+PACKAGE_BEFORE_PN += "${PN}-env"
+
+RPROVIDES:${PN}-env += "u-boot-default-env"
 FILES:${PN} = "/boot ${sysconfdir} ${datadir}"
+RDEPENDS:${PN} += "${PN}-env"
 
 do_deploy () {
     if [ -n "${UBOOT_CONFIG}" ]