msm: restart: Correct the DL_MODE_PROP and EDL_MODE_PROP properties

Assign proper strings to DL_MODE_PROP and EDL_MODE_PROP macros
"qcom,msm-imem-download_mode" and "qcom,msm-imem-emergency_download_mode"
for the download_mode and emergency_download_mode properties respectively.

Change-Id: Idb46558f2078d7a04b4b5b5b835fdf7ad4dc7db9
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>