Fix coccicheck warning:
  arch/powerpc/platforms/powernv/pci-sriov.c:443:7-10:
  WARNING: Unsigned expression compared with zero: win < 0
  arch/powerpc/platforms/powernv/pci-sriov.c:462:7-10:
  WARNING: Unsigned expression compared with zero: win < 0
Fixes: 39efc03e3ee8 ("powerpc/powernv/sriov: Move M64 BAR allocation into a helper")
Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1605007170-22171-1-git-send-email-kaixuxia@tencent.com
 {
        struct pnv_iov_data   *iov;
        struct pnv_phb        *phb;
-       unsigned int           win;
+       int                    win;
        struct resource       *res;
        int                    i, j;
        int64_t                rc;