ARM: dts: msm: Support download mode through secure I/O on MSM8909

Add the TCSR_BOOT_MISC_DETECT register address to the
qcom,pshold device on MSM8909, to allow configuring
download mode/EDL by means of a secure IO call rather
than a direct SCM call.

Change-Id: Ic1dabe6d3c828525dbdd200b3e29126376f7e327
Signed-off-by: Kishan Kumar <kishank@codeaurora.org>