USB: EHCI: fix build error in ehci-platform.c under PowerPC

This patch (as1628) fixes a build error in the ehci-platform driver
when compiled for the PowerPC architecture.  The error was introduced
by commit 99f91934a907df31ba878dfdd090002049dc476a (USB: EHCI: make
ehci-platform a separate driver).

The fix is simple; a few additional header-file #includes are needed.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>