pci:msm: Add support for PCIe halt Wr and Rd feature disable

Added the support for disabling the PCIe halt write and read feature.
By default PCIe halt write/read feature is enabled and through
device tree flag, PCIe halt Wr/Rd feature can be disabled.

In some targets reported throughput degradation due to PCIe latencies with
PCIe halt write/read feature. So, provided the support to enable and
disable PCIe halt feature.

Change-Id: I83813571bedd0a0399f4ab473e6ddfbb975c8fe4
Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@quicinc.com>