msm: pcie: Add tcsr configuration

Add support for reading tcsr configuration from device tree and
configuring tcsr register dynamically.
This change for supporting sa8195p PCIe1. The default PCIe linkage
status of PCIe1 and 2 on sa8195p is:
PCIe1: not enabled
PCIe2: x4 lane
When config the register TCSR_PCIEPHY_LINK_CONFIG to 0(default 1),
the linkage status becomes:
PCIe1: x2 lane
PCIe2: x2 lane
This change add the ability to read tcsr value from device tree.

Change-Id: Iac53f61a147a839772c8411993f3be233b142b56
Signed-off-by: Xiang Li <lixiang@codeaurora.org>
Signed-off-by: Nitesh Gupta <nitegupt@codeaurora.org>