PCI hotplug: Rename is_ejectable which also exists in dock.c

While it's declared static, etags points you to the wrong function
in drivers/acpi/dock.c and acpiphp_glue.c for example also makes
use of some (exported..) functions from this file.

If you trust etags and oversee the static declaration (what happened
to me) one gets totally confused...

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>