pciehp: Clean up pcie_init()

Clean up pciehp_ini(). This patch is trying to

  - Remove redundant capablity checks that were already done in PCIe
    port bus driver.
  - Separate the code only for debugging and make debug information
    easier to read.
  - Make the entire code easier to read and understand what it is doing.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>