soc: qcom: mdt_loader: Allow hash at any phdr

The assumption that the elf program header will always have the hash
segment program header at index 1 may not hold true in all cases. This
change updates the read metadata function to find the hash program header
dynamically.

Change-Id: Ic5aa0d290b24ec3273003d980fec070b9e058c4f
Signed-off-by: Siddharth Gupta <sidgup@codeaurora.org>