PCI: dwc: Clean up computing of msix_tbl

Commit 6f5e193b ("PCI: dwc: Fix dw_pcie_ep_raise_msix_irq() to get
correct MSI-X table address") overcomplicated the computation of the
msix_tbl address. Simplify it as it's simply the addr + offset. Provided
addr is (void *) already.

objdump -d shows no difference after this patch.

Link: https://lore.kernel.org/r/20200420065227.4920-1-jslaby@suse.cz


Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>