msm: pcie: add PCIe bandwidth scale table support

Based on PCIe link Gen speed, CX voltage corner and rate change
clock frequency can be scaled accordingly. Add support to
retrieve bandwidth scale table from devicetree to support
robust scaling.

Change-Id: I2b22a397edfdde8d27c1a608df61ff10748b920d
Signed-off-by: Tony Truong <truong@codeaurora.org>