Delete tests of CONFIG_OF_LIBFDT when testing CONFIG_OF_BOARD_SETUP

Since CONFIG_OF_BOARD_SETUP depends on CONFIG_OF_LIBFDT:

  config OF_BOARD_SETUP
          bool "Set up board-specific details in device tree before boot"
          depends on OF_LIBFDT
          ...

remove superfluous tests of CONFIG_OF_LIBFDT when testing for
CONFIG_OF_BOARD_SETUP.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
[trini: Typo fix: s/ifdefi/ifdef/]
Signed-off-by: Tom Rini <trini@konsulko.com>