e100: fix error recovery

A recent patch in -mm3 titled
"gregkh-pci-pci-don-t-enable-device-if-already-enabled.patch" causes
pci_enable_device() to be a no-op if the kernel thinks that the device is
already enabled.  This change breaks the PCI error recovery mechanism in
the e100 device driver, since, after PCI slot reset, the card is no longer
enabled.  This is a trivial fix for this problem.  Tested.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>