USB: ehci-fsl: Update ifdef check to work on 64-bit ppc

We need to use CONFIG_FSL_SOC_BOOKE instead of CONFIG_PPC_85xx as
CONFIG_PPC_85xx isn't defined when we build support for 64-bit embedded
FSL PPC SoCs.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>