ARM: dts: msm: Export axi sleep clocks for MDM9640

The apss_axi_clk and bimc_apss_axi_clk needs to be gated
on/off during power collapse. Therefore, export their handles
to allow pm driver control them and also make them not always
on clocks.

Change-Id: Ic514aa02888820d87bc516d61193b9caeb52af6f
Signed-off-by: Tianyi Gou <tgou@codeaurora.org>