soc: qcom: cmd-db: Add debugfs dumping file

soc: qcom: cmd-db: Add debugfs dumping file

It's useful for kernel devs to understand what resources and data is
stored inside command db. Add a file in debugufs called 'cmd-db' to dump
the memory contents and strings for resources along with their
addresses. E.g.

 Command DB DUMP
 Slave ARC (v16.0)
 -------------------------
 0x00030000: cx.lvl [00 00 10 00 40 00 80 00 c0 00 00 01 80 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00]
 0x00030004: cx.tmr
 0x00030010: mx.lvl [00 00 10 00 00 01 80 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00]
 0x00030014: mx.tmr

Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20200309185704.2491-1-swboyd@chromium.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>