arm: ti: boot: Remove environment partition

Remove "environment" partition and do not read it when booting Android
from eMMC. We don't use this partition anymore, so this is just an
unintentional leftover.

Earlier we were reading dtb file from "environment" partition to feed it
further to kernel. Now we are using dtb from FIT image ("boot" partition
contains boot_fit.img image), which can be seen from this command:

    bootm ${loadaddr}#${fdtfile}

where "#" character means we have FIT image in ${loadaddr} RAM address.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Acked-by: Praneeth Bajjuri <praneeth@ti.com>