powerpc/85xx: fix NAND boot linker scripts for -fpic

GOT is now handled the way the main u-boot.lds does it.  Without this,
the boot hangs when built with newer GCC (since 4.6).  Older toolchains
hid the issue by converting -fpic to -fPIC.

Signed-off-by: Scott Wood <scottwood@freescale.com>