mdm9640: Delete all pinctrl client references

Delete pinmux client references until they move over to the
new pinctrl bindings. This is required since msm-3.18 pinctrl
driver is based on upstream pinctrl framework which is different
from the internal frameowrk on msm-3.10

As an example the uart bindings are ported over.

Change-Id: I85f2175fef4ee2fbdafa455284cec18784d98b78
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>