misc: alcor_pci: fix inverted branch condition

misc: alcor_pci: fix inverted branch condition

This patch fixes a trivial mistake that I made in the previous attempt
in fixing the null bridge issue. The branch condition is inverted and we
should call alcor_pci_find_cap_offset() only if bridge is not null.

Reported-by: Colin Ian King <colin.king@canonical.com>
Fixes: 3ce3e45cc333 ("misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge")
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Link: https://lore.kernel.org/r/20210522043725.602179-1-ztong0001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>