msm: pcie: add support for RUMI

Supporting PCIe bus driver on RUMI requires additional reset
sequence and RUMI specific registers. Retrieve the RUMI
specific register base from devicetree. Also, ignore
PCIe PHY status check since RUMI does not support it.

Change-Id: I8dbc2394616ece6c25d6c0173c40072cfc7e79bb
Signed-off-by: Tony Truong <truong@codeaurora.org>