u-boot-fw-utils: reinstate target recipe for fw_printenv

The latest upgrade changed u-boot-fw-utils to u-boot-fw-utils-cross, which
removed the on-target fw_printenv (and fw_setenv).

Re-create the updated version of the u-boot-fw-utils recipe.

U-Boot does try to strip the fw_printenv binary by default now. To avoid
this, without patching the Makefile, we add HOSTSTRIP=true to EXTRA_OEMAKE.

The new U-Boot do also require us to configure the build for a specific
machine, thus we change the package arch.§

Signed-off-by: Anders Darander <anders@chargestorm.se>