board: samsung: e850-96: Report LDFW loading failures

board: samsung: e850-96: Report LDFW loading failures

LDFW firmware loading can fail, e.g. in case if user forgot to upload
the binary to the appropriate location (/EFI/firmware/ldfw.bin on ESP
partition). Report such errors explicitly, so that the user can notice
it early and take necessary actions. But don't return error code from
board_init() in this case, as LDFW firmware is not mandatory for board
operation and is only required for some features like TRNG.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>