soc: qcom: rmtfs-mem: Make sysfs attributes world-readable

In order to run an rmtfs daemon as an unprivileged user, that user would
need access to the phys_addr and size sysfs attributes. Sharing these
attributes with unprivileged users doesn't really leak anything
sensitive, since if you have access to physical memory, the jig is
up anyway.

Make those attributes readable by all.

Reviewed-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>