nguyenmac is suggesting you try GenericUSBXHCI.kext.
Historically, there have been two solutions used for USB3 on the ProBook 4540s.
1. AppleUSBXHCI.kext with Mieze's multiplex DSDT patch.
2. GenericUSBXHCI.kext with -gux_defer_usb2 kernel flag (without Mieze's patch)
In order to use GenericUSBXHCI.kext you need to have a DSDT without the multiplex patch. To have other things working (battery, audio, etc) would require you to patch DSDT manually using MaciASL and my ProBook DSDT patch repo, patching with all appropriate patches, omitting the multiplex patch.
For most people, solution #1 works fine (better than #2). Maybe your OS X install isn't vanilla? Did you download it from the Mac App Store?