payloads/tianocore: Fix check for custom bootsplash

-n needs to check against a string, but if CONFIG_TIANOCORE_BOOTSPLASH_FILE
is unset, then $(CONFIG_TIANOCORE_BOOTSPLASH_FILE) evaluates to nothing
and the check fails, leading the Makefile to try and copy a non-
existant file/path.

Change-Id: Iff717dd48748cff16f485bafaa91c7a225fb5bdb
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40860
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

0 files changed, 0 insertions, 0 deletions