board: samsung: e850-96: Load LDFW from EFI partition

board: samsung: e850-96: Load LDFW from EFI partition

In case when EFI System Partition is present it can be used to store
firmware binaries, instead of keeping those on separate dedicated
partitions. That simplifies the partition table and makes it more
standard. Rework the firmware loader code to look for LDFW binary at
/EFI/firmware/ldfw.bin on ESP first, and if either the partition or the
file doesn't exist -- fallback to reading it from 'ldfw' partition. This
way backward compatibility can be kept, and Android partition tables
without ESP partition can be handled too.

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