PCI: mobiveil: Fix struct mobiveil_pcie.pcie_reg_base address type

The field pcie_reg_base in struct mobiveil_pcie represents a physical
address so it should be of phys_addr_t type rather than void __iomem*;
this results in the following compilation  warnings:

drivers/pci/controller/pcie-mobiveil.c: In function
'mobiveil_pcie_parse_dt':
drivers/pci/controller/pcie-mobiveil.c:326:22: warning: assignment makes
pointer from integer without a cast [-Wint-conversion]
  pcie->pcie_reg_base = res->start;
                      ^
drivers/pci/controller/pcie-mobiveil.c: In function
'mobiveil_pcie_enable_msi':
drivers/pci/controller/pcie-mobiveil.c:485:25: warning: initialization
makes integer from pointer without a cast [-Wint-conversion]
  phys_addr_t msg_addr = pcie->pcie_reg_base;
                         ^~~~
drivers/pci/controller/pcie-mobiveil.c: In function
'mobiveil_compose_msi_msg':
drivers/pci/controller/pcie-mobiveil.c:640:21: warning: initialization
makes integer from pointer without a cast [-Wint-conversion]
  phys_addr_t addr = pcie->pcie_reg_base + (data->hwirq * sizeof(int));

Fix the type and with it the compilation warnings.

Fixes: 9af6bcb1 ("PCI: mobiveil: Add Mobiveil PCIe Host Bridge IP
driver")
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Subrahmanya Lingappa <l.subrahmanya@mobiveil.co.in>