env: Relocate env drivers if manual reloc is required

Relocate env drivers if manual relocation is enabled. This
patch fixes the issue of u-boot hang incase if env is
present in any of the flash devices.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>