ARM: dts: msm: Disable the spmi bus node for sm6150 rumi

As the PMIC is not present on the rumi, disable the spmi bus
node to avoid the un-successful PMIC read/writes from the
clients.

Change-Id: Ie2633101ae4778c4f43e5d1dba2f9b19e0fd4003
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>