e1000e: fix pci-device enable-counter balance

This patch removes redundant and unbalanced pci_disable_device() from
__e1000_shutdown(). pci_clear_master() is enough, device can go into
suspended state with elevated enable_cnt.

Bug was introduced in commit 23606cf5


("e1000e / PCI / PM: Add basic runtime PM support (rev. 4)") in v2.6.35

Cc: Bruce Allan <bruce.w.allan@intel.com>
CC: Stable <stable@kernel.org>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Borislav Petkov <bp@suse.de>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>