ARM: dts: msm: Add vls_clamp_reg for SM6150

For qmp phy to operate in autonomous mode it is required
to add vls_clamp_reg base address so that driver can program
the clamp register.

Change-Id: I6eab440809907f92a0490a780f2a41c5ae56a2d7
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>