omap3_evm: Let CONFIG_EFI_PARTITION be set for SPL

The #ifdef here is not enough to stop part_efi.c from being built, only
being unused.  And with recent changes this now leads to warnings.  The
easiest solution here is to just let the garbage collection at link time
do its job.

Signed-off-by: Tom Rini <trini@ti.com>