PCI: iproc: Remove redundant null pointer checking

The callers never pass a null "pcie" pointer (they check for kzalloc
failure), so we don't need to check here.  The bus driver should never call
the probe function with a null ->dev pointer, so we don't need to check
that either.  No functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>