msm_serial_hs_lite: Add devicetree support

Support to retrieve iomem resources by name does not currently
exist in device tree, access these by index until support for
this comes in.

Clocks are still queried by direct name from the driver until
device tree clock support is implemented.

Change-Id: I6e4e7d7968573959f652abb950729b851fe491b8
Signed-off-by: Sathish Ambley <sambley@codeaurora.org>