irqchip/ls-scfg-msi: Add MSI affinity support

For LS1046a and LS1043a v1.1, the MSI controller has 4 MSIRs and 4 GIC
SPI interrupts which can be associated with different Core.
So we can support affinity to improve the performance.
The MSI message data is a byte for Layerscape MSI.
  7    6   5  4  3  2   1   0
| - |       IBS       |  SRS |
SRS bit0-1 is to select a MSIR which is associated with a CPU.
IBS bit2-6 of ls1046, bit2-4 of ls1043a v1.1 is to select bit of the
MSIR. With affinity, only bits of MSIR0(srs=0 cpu0) are available.
All other bits of the MSIR1-3(cpu1-3) are reserved. The MSI hwirq
always equals bit index of the MSIR0. When changing affinity, MSI
message data will be appended corresponding SRS then MSI will be
moved to the corresponding core.
But in affinity mode, there is only 8 MSI interrupts for a controller
of LS1043a v1.1. It cannot meet the requirement of the some PCIe
devices such as 4 ports Ethernet card. In contrast, without affinity,
all MSIRs can be used for core 0, the MSI interrupts can up to 32.
So the parameter is added to control affinity mode.
"lsmsi=no-affinity" will disable affinity and increase MSI
interrupt number.

Signed-off-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>