msm: msi: support multiple dedicated PCIe IRQ for SNPS MSI

Each Synopsys MSI group (32 MSIs) is mapped to a dedicated PCIe
IRQ. Current MSI driver handles only 1 PCIe IRQ. Add support in
PCIe MSI driver to correctly handle multiple Synopsys MSI groups.

Change-Id: I7327ae49d03503f4dada7726ee0969bf79fe3b45
Signed-off-by: Tony Truong <truong@codeaurora.org>